124-486: A bole hill (also spelt bail hill ) was a place where lead was formerly smelted in the open air. The bole was usually situated at or near the top of a hill where the wind was strong. Totley Bole Hill on the western fringes of Sheffield consisted of a long low wall with two shorter walls at right angles to it at each end. At the base of a bole 20 feet (6.1 m) long were laid great trees called blocks. On these were laid blackwork , partly smelted ore about half
248-402: A displacement R AB , Newton's law of gravitation states that each object exerts a gravitational force on the other, of magnitude where G is the universal gravitational constant . The above statement may be reformulated in the following way: if g is the magnitude at a given location in a gravitational field, then the gravitational force on an object with gravitational mass M is This
372-405: A gravitational field . If a first body of mass m A is placed at a distance r (center of mass to center of mass) from a second body of mass m B , each body is subject to an attractive force F g = Gm A m B / r , where G = 6.67 × 10 N⋅kg ⋅m is the "universal gravitational constant ". This is sometimes referred to as gravitational mass. Repeated experiments since
496-411: A measure of the body's inertia , meaning the resistance to acceleration (change of velocity ) when a net force is applied. The object's mass also determines the strength of its gravitational attraction to other bodies. The SI base unit of mass is the kilogram (kg). In physics , mass is not the same as weight , even though mass is often determined by measuring the object's weight using
620-529: A spring scale , rather than balance scale comparing it directly with known masses. An object on the Moon would weigh less than it does on Earth because of the lower gravity, but it would still have the same mass. This is because weight is a force, while mass is the property that (along with gravity) determines the strength of this force. In the Standard Model of physics, the mass of elementary particles
744-406: A bronze ball and a wooden ramp. The wooden ramp was "12 cubits long, half a cubit wide and three finger-breadths thick" with a straight, smooth, polished groove . The groove was lined with " parchment , also smooth and polished as possible". And into this groove was placed "a hard, smooth and very round bronze ball". The ramp was inclined at various angles to slow the acceleration enough so that
868-534: A curved path. "For a stone projected is by the pressure of its own weight forced out of the rectilinear path, which by the projection alone it should have pursued, and made to describe a curve line in the air; and through that crooked way is at last brought down to the ground. And the greater the velocity is with which it is projected, the farther it goes before it falls to the Earth." Newton further reasons that if an object were "projected in an horizontal direction from
992-433: A density of 11.34 g/cm , which is greater than that of common metals such as iron (7.87 g/cm ), copper (8.93 g/cm ), and zinc (7.14 g/cm ). This density is the origin of the idiom to go over like a lead balloon . Some rarer metals are denser: tungsten and gold are both at 19.3 g/cm , and osmium —the densest metal known—has a density of 22.59 g/cm , almost twice that of lead. Lead
1116-492: A few radioactive isotopes. One of them is lead-210; although it has a half-life of only 22.2 years, small quantities occur in nature because lead-210 is produced by a long decay series that starts with uranium-238 (that has been present for billions of years on Earth). Lead-211, −212, and −214 are present in the decay chains of uranium-235, thorium-232, and uranium-238, respectively, so traces of all three of these lead isotopes are found naturally. Minute traces of lead-209 arise from
1240-513: A force from a scale or the surface of a planetary body such as the Earth or the Moon . This force keeps the object from going into free fall. Weight is the opposing force in such circumstances and is thus determined by the acceleration of free fall. On the surface of the Earth, for example, an object with a mass of 50 kilograms weighs 491 newtons, which means that 491 newtons is being applied to keep
1364-399: A friend, Edmond Halley , that he had solved the problem of gravitational orbits, but had misplaced the solution in his office. After being encouraged by Halley, Newton decided to develop his ideas about gravity and publish all of his findings. In November 1684, Isaac Newton sent a document to Edmund Halley, now lost but presumed to have been titled De motu corporum in gyrum (Latin for "On
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#17327946061761488-421: A gravitational field. Newton further assumed that the strength of each object's gravitational field would decrease according to the square of the distance to that object. If a large collection of small objects were formed into a giant spherical body such as the Earth or Sun, Newton calculated the collection would create a gravitational field proportional to the total mass of the body, and inversely proportional to
1612-406: A hammer and a feather are dropped from the same height through the air on Earth, the feather will take much longer to reach the ground; the feather is not really in free -fall because the force of air resistance upwards against the feather is comparable to the downward force of gravity. On the other hand, if the experiment is performed in a vacuum , in which there is no air resistance, the hammer and
1736-558: A neutron and become thallium-204; this undergoes beta decay to give stable lead-204; on capturing another neutron, it becomes lead-205, which has a half-life of around 17 million years. Further captures result in lead-206, lead-207, and lead-208. On capturing another neutron, lead-208 becomes lead-209, which quickly decays into bismuth-209. On capturing another neutron, bismuth-209 becomes bismuth-210, and this beta decays to polonium-210, which alpha decays to lead-206. The cycle hence ends at lead-206, lead-207, lead-208, and bismuth-209. In
1860-466: A polyhedral vertex and contributes two electrons to each covalent bond along an edge from their sp hybrid orbitals, the other two being an external lone pair . They may be made in liquid ammonia via the reduction of lead by sodium . Lead can form multiply-bonded chains , a property it shares with its lighter homologs in the carbon group. Its capacity to do so is much less because the Pb–Pb bond energy
1984-437: A significant partial positive charge on lead. The result is a stronger contraction of the lead 6s orbital than is the case for the 6p orbital, making it rather inert in ionic compounds. The inert pair effect is less applicable to compounds in which lead forms covalent bonds with elements of similar electronegativity, such as carbon in organolead compounds. In these, the 6s and 6p orbitals remain similarly sized and sp hybridization
2108-438: A single decay chain). In total, 43 lead isotopes have been synthesized, with mass numbers 178–220. Lead-205 is the most stable radioisotope, with a half-life of around 1.70 × 10 years. The second-most stable is lead-202, which has a half-life of about 52,500 years, longer than any of the natural trace radioisotopes. Bulk lead exposed to moist air forms a protective layer of varying composition. Lead(II) carbonate
2232-468: A string, does the combined system fall faster because it is now more massive, or does the lighter body in its slower fall hold back the heavier body? The only convincing resolution to this question is that all bodies must fall at the same rate. A later experiment was described in Galileo's Two New Sciences published in 1638. One of Galileo's fictional characters, Salviati, describes an experiment using
2356-452: A structure, with every alternate layer of oxygen atoms absent. Negative oxidation states can occur as Zintl phases , as either free lead anions, as in Ba 2 Pb, with lead formally being lead(−IV), or in oxygen-sensitive ring-shaped or polyhedral cluster ions such as the trigonal bipyramidal Pb 5 ion, where two lead atoms are lead(−I) and three are lead(0). In such anions, each atom is at
2480-410: A uniform acceleration and a uniform gravitational field. Thus, the theory postulates that the force acting on a massive object caused by a gravitational field is a result of the object's tendency to move in a straight line (in other words its inertia) and should therefore be a function of its inertial mass and the strength of the gravitational field. In theoretical physics , a mass generation mechanism
2604-460: A vacuum, as David Scott did on the surface of the Moon during Apollo 15 . A stronger version of the equivalence principle, known as the Einstein equivalence principle or the strong equivalence principle , lies at the heart of the general theory of relativity . Einstein's equivalence principle states that within sufficiently small regions of spacetime, it is impossible to distinguish between
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#17327946061762728-446: A yard thick. Then came ten or twelve trees called shankards . On top of these three or four courses of fire trees were laid with fresh ore. This was ignited and burnt for about 48 hours. This smelted lead, which ran down channels provided for the purpose and was cast into sows of about 11 hundredweight . A single firing produced 16 fothers of lead (about 18 tons ) from 160 loads of ore (about 40 tons) and 30 tons of wood. Much of
2852-590: Is 6 times higher, copper 10 times, and mild steel 15 times higher); it can be strengthened by adding small amounts of copper or antimony . The melting point of lead—at 327.5 °C (621.5 °F) —is very low compared to most metals. Its boiling point of 1749 °C (3180 °F) is the lowest among the carbon-group elements. The electrical resistivity of lead at 20 °C is 192 nanoohm -meters, almost an order of magnitude higher than those of other industrial metals (copper at 15.43 nΩ·m ; gold 20.51 nΩ·m ; and aluminium at 24.15 nΩ·m ). Lead
2976-485: Is a balance scale , which balances the force of one object's weight against the force of another object's weight. The two sides of a balance scale are close enough that the objects experience similar gravitational fields. Hence, if they have similar masses then their weights will also be similar. This allows the scale, by comparing weights, to also compare masses. Consequently, historical weight standards were often defined in terms of amounts. The Romans, for example, used
3100-521: Is a chemical element ; it has symbol Pb (from Latin plumbum ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable , and also has a relatively low melting point . When freshly cut, lead is a shiny gray with a hint of blue. It tarnishes to a dull gray color when exposed to air. Lead has the highest atomic number of any stable element and three of its isotopes are endpoints of major nuclear decay chains of heavier elements. Lead
3224-520: Is a neurotoxin that accumulates in soft tissues and bones. It damages the nervous system and interferes with the function of biological enzymes , causing neurological disorders ranging from behavioral problems to brain damage, and also affects general health, cardiovascular, and renal systems. Lead's toxicity was first documented by ancient Greek and Roman writers, who noted some of the symptoms of lead poisoning , but became widely recognized in Europe in
3348-401: Is a superconductor at temperatures lower than 7.19 K ; this is the highest critical temperature of all type-I superconductors and the third highest of the elemental superconductors. Natural lead consists of four stable isotopes with mass numbers of 204, 206, 207, and 208, and traces of six short-lived radioisotopes with mass numbers 209–214 inclusive. The high number of isotopes
3472-420: Is a common constituent; the sulfate or chloride may also be present in urban or maritime settings. This layer makes bulk lead effectively chemically inert in the air. Finely powdered lead, as with many metals, is pyrophoric , and burns with a bluish-white flame. Fluorine reacts with lead at room temperature, forming lead(II) fluoride . The reaction with chlorine is similar but requires heating, as
3596-780: Is a mixed sulfide derived from galena; anglesite , PbSO 4 , is a product of galena oxidation; and cerussite or white lead ore, PbCO 3 , is a decomposition product of galena. Arsenic , tin , antimony , silver , gold , copper , bismuth are common impurities in lead minerals. World lead resources exceed two billion tons. Significant deposits are located in Australia, China, Ireland, Mexico, Peru, Portugal, Russia, United States. Global reserves—resources that are economically feasible to extract—totaled 88 million tons in 2016, of which Australia had 35 million, China 17 million, Russia 6.4 million. Typical background concentrations of lead do not exceed 0.1 μg/m in
3720-420: Is a relatively unreactive post-transition metal . Its weak metallic character is illustrated by its amphoteric nature; lead and lead oxides react with acids and bases , and it tends to form covalent bonds . Compounds of lead are usually found in the +2 oxidation state rather than the +4 state common with lighter members of the carbon group . Exceptions are mostly limited to organolead compounds . Like
3844-426: Is a strong oxidizing agent, capable of oxidizing hydrochloric acid to chlorine gas. This is because the expected PbCl 4 that would be produced is unstable and spontaneously decomposes to PbCl 2 and Cl 2 . Analogously to lead monoxide , lead dioxide is capable of forming plumbate anions. Lead disulfide and lead diselenide are only stable at high pressures. Lead tetrafluoride , a yellow crystalline powder,
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3968-450: Is a theory which attempts to explain the origin of mass from the most fundamental laws of physics . To date, a number of different models have been proposed which advocate different views of the origin of mass. The problem is complicated by the fact that the notion of mass is strongly related to the gravitational interaction but a theory of the latter has not been yet reconciled with the currently popular model of particle physics , known as
4092-404: Is a very soft metal with a Mohs hardness of 1.5; it can be scratched with a fingernail. It is quite malleable and somewhat ductile. The bulk modulus of lead—a measure of its ease of compressibility—is 45.8 GPa . In comparison, that of aluminium is 75.2 GPa; copper 137.8 GPa; and mild steel 160–169 GPa. Lead's tensile strength , at 12–17 MPa, is low (that of aluminium
4216-419: Is adequate for most of classical mechanics, and sometimes remains in use in basic education, if the priority is to teach the difference between mass from weight.) This traditional "amount of matter" belief was contradicted by the fact that different atoms (and, later, different elementary particles) can have different masses, and was further contradicted by Einstein's theory of relativity (1905), which showed that
4340-561: Is believed to be a result of their coupling with the Higgs boson in what is known as the Brout–Englert–Higgs mechanism . There are several distinct phenomena that can be used to measure mass. Although some theorists have speculated that some of these phenomena could be independent of each other, current experiments have found no difference in results regardless of how it is measured: The mass of an object determines its acceleration in
4464-445: Is common for the carbon group. The divalent state is rare for carbon and silicon , minor for germanium, important (but not prevailing) for tin, and is the more important of the two oxidation states for lead. This is attributable to relativistic effects , specifically the inert pair effect , which manifests itself when there is a large difference in electronegativity between lead and oxide , halide , or nitride anions, leading to
4588-408: Is consistent with lead's atomic number being even. Lead has a magic number of protons (82), for which the nuclear shell model accurately predicts an especially stable nucleus. Lead-208 has 126 neutrons, another magic number, which may explain why lead-208 is extraordinarily stable. With its high atomic number, lead is the heaviest element whose natural isotopes are regarded as stable; lead-208
4712-414: Is exploited in the synthesis of other lead compounds. Few inorganic lead(IV) compounds are known. They are only formed in highly oxidizing solutions and do not normally exist under standard conditions. Lead(II) oxide gives a mixed oxide on further oxidation, Pb 3 O 4 . It is described as lead(II,IV) oxide , or structurally 2PbO·PbO 2 , and is the best-known mixed valence lead compound. Lead dioxide
4836-502: Is more prevalent than most other elements with atomic numbers greater than 40. Primordial lead—which comprises the isotopes lead-204, lead-206, lead-207, and lead-208—was mostly created as a result of repetitive neutron capture processes occurring in stars. The two main modes of capture are the s- and r-processes . In the s-process (s is for "slow"), captures are separated by years or decades, allowing less stable nuclei to undergo beta decay . A stable thallium-203 nucleus can capture
4960-650: Is not stable, as both the lead(III) ion and the larger complexes containing it are radicals . The same applies for lead(I), which can be found in such radical species. Numerous mixed lead(II,IV) oxides are known. When PbO 2 is heated in air, it becomes Pb 12 O 19 at 293 °C, Pb 12 O 17 at 351 °C, Pb 3 O 4 at 374 °C, and finally PbO at 605 °C. A further sesquioxide , Pb 2 O 3 , can be obtained at high pressure, along with several non-stoichiometric phases. Many of them show defective fluorite structures in which some oxygen atoms are replaced by vacancies: PbO can be considered as having such
5084-741: Is over three and a half times lower than that of the C–C bond . With itself, lead can build metal–metal bonds of an order up to three. With carbon, lead forms organolead compounds similar to, but generally less stable than, typical organic compounds (due to the Pb–C bond being rather weak). This makes the organometallic chemistry of lead far less wide-ranging than that of tin. Lead predominantly forms organolead(IV) compounds, even when starting with inorganic lead(II) reactants; very few organolead(II) compounds are known. The most well-characterized exceptions are Pb[CH(SiMe 3 ) 2 ] 2 and plumbocene . The lead analog of
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5208-415: Is stable, but less so than the difluoride . Lead tetrachloride (a yellow oil) decomposes at room temperature, lead tetrabromide is less stable still, and the existence of lead tetraiodide is questionable. Some lead compounds exist in formal oxidation states other than +4 or +2. Lead(III) may be obtained, as an intermediate between lead(II) and lead(IV), in larger organolead complexes; this oxidation state
5332-413: Is still energetically favorable. Lead, like carbon, is predominantly tetravalent in such compounds. There is a relatively large difference in the electronegativity of lead(II) at 1.87 and lead(IV) at 2.33. This difference marks the reversal in the trend of increasing stability of the +4 oxidation state going down the carbon group; tin, by comparison, has values of 1.80 in the +2 oxidation state and 1.96 in
5456-408: Is the acceleration due to Earth's gravitational field , (expressed as the acceleration experienced by a free-falling object). For other situations, such as when objects are subjected to mechanical accelerations from forces other than the resistance of a planetary surface, the weight force is proportional to the mass of an object multiplied by the total acceleration away from free fall, which is called
5580-430: Is the basis by which masses are determined by weighing . In simple spring scales , for example, the force F is proportional to the displacement of the spring beneath the weighing pan, as per Hooke's law , and the scales are calibrated to take g into account, allowing the mass M to be read off. Assuming the gravitational field is equivalent on both sides of the balance, a balance measures relative weight, giving
5704-427: Is the gravitational mass ( standard gravitational parameter ) of the body causing gravitational fields, and R is the radial coordinate (the distance between the centers of the two bodies). By finding the exact relationship between a body's gravitational mass and its gravitational field, Newton provided a second method for measuring gravitational mass. The mass of the Earth can be determined using Kepler's method (from
5828-448: Is the heaviest stable nucleus. (This distinction formerly fell to bismuth , with an atomic number of 83, until its only primordial isotope , bismuth-209, was found in 2003 to decay very slowly.) The four stable isotopes of lead could theoretically undergo alpha decay to isotopes of mercury with a release of energy, but this has not been observed for any of them; their predicted half-lives range from 10 to 10 years (at least 10 times
5952-538: Is the origin of the English word " plumbing ". Its ease of working, its low melting point enabling the easy fabrication of completely waterproof welded joints, and its resistance to corrosion ensured its widespread use in other applications, including pharmaceuticals, roofing, currency, warfare. Writers of the time, such as Cato the Elder , Columella , and Pliny the Elder , recommended lead (and lead-coated) vessels for
6076-525: Is the so-called inert pair effect : the 6s electrons of lead become reluctant to participate in bonding, stabilising the +2 oxidation state and making the distance between nearest atoms in crystalline lead unusually long. Lead's lighter carbon group congeners form stable or metastable allotropes with the tetrahedrally coordinated and covalently bonded diamond cubic structure. The energy levels of their outer s- and p-orbitals are close enough to allow mixing into four hybrid sp orbitals. In lead,
6200-410: Is theoretically possible to collect an immense number of small objects and form them into an enormous gravitating sphere. However, from a practical standpoint, the gravitational fields of small objects are extremely weak and difficult to measure. Newton's books on universal gravitation were published in the 1680s, but the first successful measurement of the Earth's mass in terms of traditional mass units,
6324-603: Is to us. Heinz Eschnauer and Markus Stoeppler "Wine—An enological specimen bank", 1992 Mass Mass is an intrinsic property of a body . It was traditionally believed to be related to the quantity of matter in a body, until the discovery of the atom and particle physics . It was found that different atoms and different elementary particles , theoretically with the same amount of matter, have nonetheless different masses. Mass in modern physics has multiple definitions which are conceptually distinct, but physically equivalent. Mass can be experimentally defined as
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#17327946061766448-446: Is usefully exploited: lead tetraacetate is an important laboratory reagent for oxidation in organic synthesis. Tetraethyllead, once added to automotive gasoline, was produced in larger quantities than any other organometallic compound, and is still widely used in fuel for small aircraft . Other organolead compounds are less chemically stable. For many organic compounds, a lead analog does not exist. Lead's per-particle abundance in
6572-467: The Cavendish experiment , did not occur until 1797, over a hundred years later. Henry Cavendish found that the Earth's density was 5.448 ± 0.033 times that of water. As of 2009, the Earth's mass in kilograms is only known to around five digits of accuracy, whereas its gravitational mass is known to over nine significant figures. Given two objects A and B, of masses M A and M B , separated by
6696-630: The Phoenicians worked deposits in the Iberian peninsula ; by 1600 BC, lead mining existed in Cyprus , Greece , and Sardinia . Rome's territorial expansion in Europe and across the Mediterranean, and its development of mining, led to it becoming the greatest producer of lead during the classical era , with an estimated annual output peaking at 80,000 tonnes. Like their predecessors,
6820-671: The Solar System is 0.121 ppb (parts per billion). This figure is two and a half times higher than that of platinum , eight times more than mercury , and seventeen times more than gold . The amount of lead in the universe is slowly increasing as most heavier atoms (all of which are unstable) gradually decay to lead. The abundance of lead in the Solar System since its formation 4.5 billion years ago has increased by about 0.75%. The solar system abundances table shows that lead, despite its relatively high atomic number,
6944-483: The Solar System . On 25 August 1609, Galileo Galilei demonstrated his first telescope to a group of Venetian merchants, and in early January 1610, Galileo observed four dim objects near Jupiter, which he mistook for stars. However, after a few days of observation, Galileo realized that these "stars" were in fact orbiting Jupiter. These four objects (later named the Galilean moons in honor of their discoverer) were
7068-550: The Standard Model . The concept of amount is very old and predates recorded history . The concept of "weight" would incorporate "amount" and acquire a double meaning that was not clearly recognized as such. What we now know as mass was until the time of Newton called “weight.” ... A goldsmith believed that an ounce of gold was a quantity of gold. ... But the ancients believed that a beam balance also measured “heaviness” which they recognized through their muscular senses. ... Mass and its associated downward force were believed to be
7192-405: The carob seed ( carat or siliqua ) as a measurement standard. If an object's weight was equivalent to 1728 carob seeds , then the object was said to weigh one Roman pound. If, on the other hand, the object's weight was equivalent to 144 carob seeds then the object was said to weigh one Roman ounce (uncia). The Roman pound and ounce were both defined in terms of different sized collections of
7316-495: The elementary charge . Non-SI units accepted for use with SI units include: Outside the SI system, other units of mass include: In physical science , one may distinguish conceptually between at least seven different aspects of mass , or seven physical notions that involve the concept of mass . Every experiment to date has shown these seven values to be proportional , and in some cases equal, and this proportionality gives rise to
7440-804: The fall of Rome and did not reach comparable levels until the Industrial Revolution . Lead played a crucial role in the development of the printing press , as movable type could be relatively easily cast from lead alloys. In 2014, the annual global production of lead was about ten million tonnes, over half of which was from recycling. Lead's high density, low melting point, ductility and relative inertness to oxidation make it useful. These properties, combined with its relative abundance and low cost, resulted in its extensive use in construction , plumbing , batteries , bullets , shots , weights , solders , pewters , fusible alloys , lead paints , leaded gasoline , and radiation shielding . Lead
7564-442: The melting point of ice. However, because precise measurement of a cubic decimetre of water at the specified temperature and pressure was difficult, in 1889 the kilogram was redefined as the mass of a metal object, and thus became independent of the metre and the properties of water, this being a copper prototype of the grave in 1793, the platinum Kilogramme des Archives in 1799, and the platinum–iridium International Prototype of
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#17327946061767688-401: The nucleus , and more shielded by smaller orbitals. The sum of the first four ionization energies of lead exceeds that of tin, contrary to what periodic trends would predict. This is explained by relativistic effects , which become significant in heavier atoms, which contract s and p orbitals such that lead's 6s electrons have larger binding energies than its 5s electrons. A consequence
7812-416: The proper acceleration . Through such mechanisms, objects in elevators, vehicles, centrifuges, and the like, may experience weight forces many times those caused by resistance to the effects of gravity on objects, resulting from planetary surfaces. In such cases, the generalized equation for weight W of an object is related to its mass m by the equation W = – ma , where a is the proper acceleration of
7936-453: The torsion balance pendulum, in 1889. As of 2008 , no deviation from universality, and thus from Galilean equivalence, has ever been found, at least to the precision 10 . More precise experimental efforts are still being carried out. The universality of free-fall only applies to systems in which gravity is the only acting force. All other forces, especially friction and air resistance , must be absent or at least negligible. For example, if
8060-444: The "Galilean equivalence principle" or the " weak equivalence principle " has the most important consequence for freely falling objects. Suppose an object has inertial and gravitational masses m and M , respectively. If the only force acting on the object comes from a gravitational field g , the force on the object is: Given this force, the acceleration of the object can be determined by Newton's second law: Putting these together,
8184-468: The +4 state. Lead(II) compounds are characteristic of the inorganic chemistry of lead. Even strong oxidizing agents like fluorine and chlorine react with lead to give only PbF 2 and PbCl 2 . Lead(II) ions are usually colorless in solution, and partially hydrolyze to form Pb(OH) and finally [Pb 4 (OH) 4 ] (in which the hydroxyl ions act as bridging ligands ), but are not reducing agents as tin(II) ions are. Techniques for identifying
8308-400: The 17th century have demonstrated that inertial and gravitational mass are identical; since 1915, this observation has been incorporated a priori in the equivalence principle of general relativity . The International System of Units (SI) unit of mass is the kilogram (kg). The kilogram is 1000 grams (g), and was first defined in 1795 as the mass of one cubic decimetre of water at
8432-626: The Egyptians had used lead for sinkers in fishing nets , glazes , glasses , enamels , ornaments . Various civilizations of the Fertile Crescent used lead as a writing material , as coins , and as a construction material . Lead was used by the ancient Chinese as a stimulant , as currency , as contraceptive , and in chopsticks . The Indus Valley civilization and the Mesoamericans used it for making amulets ; and
8556-675: The Kilogram (IPK) in 1889. However, the mass of the IPK and its national copies have been found to drift over time. The re-definition of the kilogram and several other units came into effect on 20 May 2019, following a final vote by the CGPM in November 2018. The new definition uses only invariant quantities of nature: the speed of light , the caesium hyperfine frequency , the Planck constant and
8680-475: The Romans obtained lead mostly as a by-product of silver smelting. Lead mining occurred in central Europe , Britain , Balkans , Greece , Anatolia , Hispania , the latter accounting for 40% of world production. Lead tablets were commonly used as a material for letters. Lead coffins, cast in flat sand forms and with interchangeable motifs to suit the faith of the deceased, were used in ancient Judea . Lead
8804-428: The abstract concept of mass. There are a number of ways mass can be measured or operationally defined : In everyday usage, mass and " weight " are often used interchangeably. For instance, a person's weight may be stated as 75 kg. In a constant gravitational field, the weight of an object is proportional to its mass, and it is unproblematic to use the same unit for both concepts. But because of slight differences in
8928-607: The atmosphere; 100 mg/kg in soil; 4 mg/kg in vegetation, 5 μg/L in fresh water and seawater. The modern English word lead is of Germanic origin; it comes from the Middle English leed and Old English lēad (with the macron above the "e" signifying that the vowel sound of that letter is long). The Old English word is derived from the hypothetical reconstructed Proto-Germanic * lauda- ('lead'). According to linguistic theory, this word bore descendants in multiple Germanic languages of exactly
9052-405: The classical theory offers no compelling reason why the gravitational mass has to equal the inertial mass. That it does is merely an empirical fact. Albert Einstein developed his general theory of relativity starting with the assumption that the inertial and passive gravitational masses are the same. This is known as the equivalence principle . The particular equivalence often referred to as
9176-437: The course of the Earth's history, have remained in the crust instead of sinking deeper into the Earth's interior. This accounts for lead's relatively high crustal abundance of 14 ppm; it is the 36th most abundant element in the crust. The main lead-bearing mineral is galena (PbS), which is mostly found with zinc ores. Most other lead minerals are related to galena in some way; boulangerite , Pb 5 Sb 4 S 11 ,
9300-419: The current age of the universe). Three of the stable isotopes are found in three of the four major decay chains : lead-206, lead-207, and lead-208 are the final decay products of uranium-238 , uranium-235 , and thorium-232 , respectively. These decay chains are called the uranium chain , the actinium chain , and the thorium chain . Their isotopic concentrations in a natural rock sample depends greatly on
9424-428: The diiodide . Many lead(II) pseudohalides are known, such as the cyanide, cyanate, and thiocyanate . Lead(II) forms an extensive variety of halide coordination complexes , such as [PbCl 4 ] , [PbCl 6 ] , and the [Pb 2 Cl 9 ] n chain anion. Lead(II) sulfate is insoluble in water, like the sulfates of other heavy divalent cations . Lead(II) nitrate and lead(II) acetate are very soluble, and this
9548-470: The double of the distance between the two bodies. Hooke urged Newton, who was a pioneer in the development of calculus , to work through the mathematical details of Keplerian orbits to determine if Hooke's hypothesis was correct. Newton's own investigations verified that Hooke was correct, but due to personal differences between the two men, Newton chose not to reveal this to Hooke. Isaac Newton kept quiet about his discoveries until 1684, at which time he told
9672-525: The eastern and southern Africans used lead in wire drawing . Because silver was extensively used as a decorative material and an exchange medium, lead deposits came to be worked in Asia Minor from 3000 BC; later, lead deposits were developed in the Aegean and Laurion . These three regions collectively dominated production of mined lead until c. 1200 BC . Beginning c. 2000 BC,
9796-434: The elapsed time could be measured. The ball was allowed to roll a known distance down the ramp, and the time taken for the ball to move the known distance was measured. The time was measured using a water clock described as follows: Galileo found that for an object in free fall, the distance that the object has fallen is always proportional to the square of the elapsed time: Galileo had shown that objects in free fall under
9920-578: The element its chemical symbol Pb . The word * ɸloud-io- is thought to be the origin of Proto-Germanic * bliwa- (which also means 'lead'), from which stemmed the German Blei . The name of the chemical element is not related to the verb of the same spelling, which is derived from Proto-Germanic * laidijan- ('to lead'). Metallic lead beads dating back to 7000–6500 BC have been found in Asia Minor and may represent
10044-497: The exact number of carob seeds that would be required to produce a gravitational field similar to that of the Earth or Sun. In fact, by unit conversion it is a simple matter of abstraction to realize that any traditional mass unit can theoretically be used to measure gravitational mass. Measuring gravitational mass in terms of traditional mass units is simple in principle, but extremely difficult in practice. According to Newton's theory, all objects produce gravitational fields and it
10168-410: The feather should hit the ground at exactly the same time (assuming the acceleration of both objects towards each other, and of the ground towards both objects, for its own part, is negligible). This can easily be done in a high school laboratory by dropping the objects in transparent tubes that have the air removed with a vacuum pump. It is even more dramatic when done in an environment that naturally has
10292-404: The first celestial bodies observed to orbit something other than the Earth or Sun. Galileo continued to observe these moons over the next eighteen months, and by the middle of 1611, he had obtained remarkably accurate estimates for their periods. Sometime prior to 1638, Galileo turned his attention to the phenomenon of objects in free fall, attempting to characterize these motions. Galileo was not
10416-413: The first example of metal smelting . At that time, lead had few (if any) applications due to its softness and dull appearance. The major reason for the spread of lead production was its association with silver, which may be obtained by burning galena (a common lead mineral). The Ancient Egyptians were the first to use lead minerals in cosmetics, an application that spread to Ancient Greece and beyond;
10540-402: The first paragraph of Principia , Newton defined quantity of matter as “density and bulk conjunctly”, and mass as quantity of matter. The quantity of matter is the measure of the same, arising from its density and bulk conjunctly. ... It is this quantity that I mean hereafter everywhere under the name of body or mass. And the same is known by the weight of each body; for it is proportional to
10664-436: The first to investigate Earth's gravitational field, nor was he the first to accurately describe its fundamental characteristics. However, Galileo's reliance on scientific experimentation to establish physical principles would have a profound effect on future generations of scientists. It is unclear if these were just hypothetical experiments used to illustrate a concept, or if they were real experiments performed by Galileo, but
10788-572: The gap between Galileo's gravitational acceleration and Kepler's elliptical orbits. It appeared in Newton's 1728 book A Treatise of the System of the World . According to Galileo's concept of gravitation, a dropped stone falls with constant acceleration down towards the Earth. However, Newton explains that when a stone is thrown horizontally (meaning sideways or perpendicular to Earth's gravity) it follows
10912-421: The gravitational acceleration is given by: This says that the ratio of gravitational to inertial mass of any object is equal to some constant K if and only if all objects fall at the same rate in a given gravitational field. This phenomenon is referred to as the "universality of free-fall". In addition, the constant K can be taken as 1 by defining our units appropriately. The first experiments demonstrating
11036-430: The group. Lead dihalides are well-characterized; this includes the diastatide and mixed halides, such as PbFCl. The relative insolubility of the latter forms a useful basis for the gravimetric determination of fluorine. The difluoride was the first solid ionically conducting compound to be discovered (in 1834, by Michael Faraday ). The other dihalides decompose on exposure to ultraviolet or visible light, especially
11160-449: The inert pair effect increases the separation between its s- and p-orbitals, and the gap cannot be overcome by the energy that would be released by extra bonds following hybridization. Rather than having a diamond cubic structure, lead forms metallic bonds in which only the p-electrons are delocalized and shared between the Pb ions. Lead consequently has a face-centered cubic structure like
11284-629: The influence of the Earth's gravitational field have a constant acceleration, and Galileo's contemporary, Johannes Kepler, had shown that the planets follow elliptical paths under the influence of the Sun's gravitational mass. However, Galileo's free fall motions and Kepler's planetary motions remained distinct during Galileo's lifetime. According to K. M. Browne: "Kepler formed a [distinct] concept of mass ('amount of matter' ( copia materiae )), but called it 'weight' as did everyone at that time." Finally, in 1686, Newton gave this distinct concept its own name. In
11408-447: The late 19th century AD. A lead atom has 82 electrons , arranged in an electron configuration of [ Xe ]4f 5d 6s 6p . The sum of lead's first and second ionization energies —the total energy required to remove the two 6p electrons—is close to that of tin , lead's upper neighbor in the carbon group . This is unusual; ionization energies generally fall going down a group, as an element's outer electrons become more distant from
11532-560: The latter being stable only above around 488 °C. Litharge is the most commonly used inorganic compound of lead. There is no lead(II) hydroxide; increasing the pH of solutions of lead(II) salts leads to hydrolysis and condensation. Lead commonly reacts with heavier chalcogens. Lead sulfide is a semiconductor , a photoconductor , and an extremely sensitive infrared radiation detector . The other two chalcogenides, lead selenide and lead telluride , are likewise photoconducting. They are unusual in that their color becomes lighter going down
11656-441: The latter is not; this allows for lead–lead dating . As uranium decays into lead, their relative amounts change; this is the basis for uranium–lead dating . Lead-207 exhibits nuclear magnetic resonance , a property that has been used to study its compounds in solution and solid state, including in the human body. Apart from the stable isotopes, which make up almost all lead that exists naturally, there are trace quantities of
11780-461: The lighter members of the group, lead tends to bond with itself ; it can form chains and polyhedral structures. Since lead is easily extracted from its ores , prehistoric people in the Near East were aware of it . Galena is a principal ore of lead which often bears silver. Interest in silver helped initiate widespread extraction and use of lead in ancient Rome . Lead production declined after
11904-558: The motion of bodies in an orbit"). Halley presented Newton's findings to the Royal Society of London, with a promise that a fuller presentation would follow. Newton later recorded his ideas in a three-book set, entitled Philosophiæ Naturalis Principia Mathematica (English: Mathematical Principles of Natural Philosophy ). The first was received by the Royal Society on 28 April 1685–86; the second on 2 March 1686–87; and
12028-403: The nearby gravitational field. No matter how strong the gravitational field, objects in free fall are weightless , though they still have mass. The force known as "weight" is proportional to mass and acceleration in all situations where the mass is accelerated away from free fall. For example, when a body is at rest in a gravitational field (rather than in free fall), it must be accelerated by
12152-539: The neutrons are arranged in complete shells in the atomic nucleus, and it becomes harder to energetically accommodate more of them. When the neutron flux subsides, these nuclei beta decay into stable isotopes of osmium , iridium , platinum . Lead is classified as a chalcophile under the Goldschmidt classification , meaning it is generally found combined with sulfur. It rarely occurs in its native , metallic form. Many lead minerals are relatively light and, over
12276-509: The object caused by all influences other than gravity. (Again, if gravity is the only influence, such as occurs when an object falls freely, its weight will be zero). Although inertial mass, passive gravitational mass and active gravitational mass are conceptually distinct, no experiment has ever unambiguously demonstrated any difference between them. In classical mechanics , Newton's third law implies that active and passive gravitational mass must always be identical (or at least proportional), but
12400-430: The object from going into free fall. By contrast, on the surface of the Moon, the same object still has a mass of 50 kilograms but weighs only 81.5 newtons, because only 81.5 newtons is required to keep this object from going into a free fall on the moon. Restated in mathematical terms, on the surface of the Earth, the weight W of an object is related to its mass m by W = mg , where g = 9.80665 m/s
12524-412: The orbit of Earth's Moon), or it can be determined by measuring the gravitational acceleration on the Earth's surface, and multiplying that by the square of the Earth's radius. The mass of the Earth is approximately three-millionths of the mass of the Sun. To date, no other accurate method for measuring gravitational mass has been discovered. Newton's cannonball was a thought experiment used to bridge
12648-412: The ore was left incompletely smelted having become blackwork . Some of this was smelted in a foot-pump blown furnace, but some was left to be used when the bole was next fired. Bole smelting was replaced by smelting in smeltmills in the late 16th century. That was in turn replaced by smelting in cupolas, a variety of reverberatory furnace in the 18th century. Lead Lead (pronounced "led")
12772-409: The planets orbit the Sun. In Kepler's final planetary model, he described planetary orbits as following elliptical paths with the Sun at a focal point of the ellipse . Kepler discovered that the square of the orbital period of each planet is directly proportional to the cube of the semi-major axis of its orbit, or equivalently, that the ratio of these two values is constant for all planets in
12896-418: The preparation of sweeteners and preservatives added to wine and food. The lead conferred an agreeable taste due to the formation of "sugar of lead" ( lead(II) acetate ), whereas copper vessels imparted a bitter flavor through verdigris formation. This metal was by far the most used material in classical antiquity, and it is appropriate to refer to the (Roman) Lead Age. Lead was to the Romans what plastic
13020-400: The presence of an applied force. The inertia and the inertial mass describe this property of physical bodies at the qualitative and quantitative level respectively. According to Newton's second law of motion , if a body of fixed mass m is subjected to a single force F , its acceleration a is given by F / m . A body's mass also determines the degree to which it generates and is affected by
13144-414: The presence of the Pb ion in water generally rely on the precipitation of lead(II) chloride using dilute hydrochloric acid. As the chloride salt is sparingly soluble in water, in very dilute solutions the precipitation of lead(II) sulfide is instead achieved by bubbling hydrogen sulfide through the solution. Lead monoxide exists in two polymorphs , litharge α-PbO (red) and massicot β-PbO (yellow),
13268-422: The presence of these three parent uranium and thorium isotopes. For example, the relative abundance of lead-208 can range from 52% in normal samples to 90% in thorium ores; for this reason, the standard atomic weight of lead is given to only one decimal place. As time passes, the ratio of lead-206 and lead-207 to lead-204 increases, since the former two are supplemented by radioactive decay of heavier elements while
13392-432: The r-process (r is for "rapid"), captures happen faster than nuclei can decay. This occurs in environments with a high neutron density, such as a supernova or the merger of two neutron stars . The neutron flux involved may be on the order of 10 neutrons per square centimeter per second. The r-process does not form as much lead as the s-process. It tends to stop once neutron-rich nuclei reach 126 neutrons. At this point,
13516-464: The relative gravitation mass of each object. Mass was traditionally believed to be a measure of the quantity of matter in a physical body, equal to the "amount of matter" in an object. For example, Barre´ de Saint-Venant argued in 1851 that every object contains a number of "points" (basically, interchangeable elementary particles), and that mass is proportional to the number of points the object contains. (In practice, this "amount of matter" definition
13640-541: The resulting chloride layer diminishes the reactivity of the elements. Molten lead reacts with the chalcogens to give lead(II) chalcogenides. Lead metal resists sulfuric and phosphoric acid but not hydrochloric or nitric acid ; the outcome depends on insolubility and subsequent passivation of the product salt. Organic acids, such as acetic acid , dissolve lead in the presence of oxygen. Concentrated alkalis dissolve lead and form plumbites . Lead shows two main oxidation states: +4 and +2. The tetravalent state
13764-554: The results obtained from these experiments were both realistic and compelling. A biography by Galileo's pupil Vincenzo Viviani stated that Galileo had dropped balls of the same material, but different masses, from the Leaning Tower of Pisa to demonstrate that their time of descent was independent of their mass. In support of this conclusion, Galileo had advanced the following theoretical argument: He asked if two bodies of different masses and different rates of fall are tied by
13888-503: The same common mass standard, the carob seed. The ratio of a Roman ounce (144 carob seeds) to a Roman pound (1728 carob seeds) was: In 1600 AD, Johannes Kepler sought employment with Tycho Brahe , who had some of the most precise astronomical data available. Using Brahe's precise observations of the planet Mars, Kepler spent the next five years developing his own method for characterizing planetary motion. In 1609, Johannes Kepler published his three laws of planetary motion, explaining how
14012-518: The same meaning. There is no consensus on the origin of the Proto-Germanic * lauda- . One hypothesis suggests it is derived from Proto-Indo-European * lAudh- ('lead'; capitalization of the vowel is equivalent to the macron). Another hypothesis suggests it is borrowed from Proto-Celtic * ɸloud-io- ('lead'). This word is related to the Latin plumbum , which gave
14136-407: The same thing. Humans, at some early era, realized that the weight of a collection of similar objects was directly proportional to the number of objects in the collection: where W is the weight of the collection of similar objects and n is the number of objects in the collection. Proportionality, by definition, implies that two values have a constant ratio : An early use of this relationship
14260-491: The similarly sized divalent metals calcium and strontium . Pure lead has a bright, shiny gray appearance with a hint of blue. It tarnishes on contact with moist air and takes on a dull appearance, the hue of which depends on the prevailing conditions. Characteristic properties of lead include high density , malleability, ductility, and high resistance to corrosion due to passivation . Lead's close-packed face-centered cubic structure and high atomic weight result in
14384-588: The simplest organic compound , methane , is plumbane . Plumbane may be obtained in a reaction between metallic lead and atomic hydrogen. Two simple derivatives, tetramethyllead and tetraethyllead , are the best-known organolead compounds. These compounds are relatively stable: tetraethyllead only starts to decompose if heated or if exposed to sunlight or ultraviolet light. With sodium metal, lead readily forms an equimolar alloy that reacts with alkyl halides to form organometallic compounds such as tetraethyllead. The oxidizing nature of many organolead compounds
14508-441: The square of the distance to the body's center. For example, according to Newton's theory of universal gravitation, each carob seed produces a gravitational field. Therefore, if one were to gather an immense number of carob seeds and form them into an enormous sphere, then the gravitational field of the sphere would be proportional to the number of carob seeds in the sphere. Hence, it should be theoretically possible to determine
14632-501: The strength of the Earth's gravitational field at different places, the distinction becomes important for measurements with a precision better than a few percent, and for places far from the surface of the Earth, such as in space or on other planets. Conceptually, "mass" (measured in kilograms ) refers to an intrinsic property of an object, whereas "weight" (measured in newtons ) measures an object's resistance to deviating from its current course of free fall , which can be influenced by
14756-500: The third on 6 April 1686–87. The Royal Society published Newton's entire collection at their own expense in May 1686–87. Isaac Newton had bridged the gap between Kepler's gravitational mass and Galileo's gravitational acceleration, resulting in the discovery of the following relationship which governed both of these: where g is the apparent acceleration of a body as it passes through a region of space where gravitational fields exist, μ
14880-492: The top of a high mountain" with sufficient velocity, "it would reach at last quite beyond the circumference of the Earth, and return to the mountain from which it was projected." In contrast to earlier theories (e.g. celestial spheres ) which stated that the heavens were made of entirely different material, Newton's theory of mass was groundbreaking partly because it introduced universal gravitational mass : every object has gravitational mass, and therefore, every object generates
15004-459: The universality of free-fall were—according to scientific 'folklore'—conducted by Galileo obtained by dropping objects from the Leaning Tower of Pisa . This is most likely apocryphal: he is more likely to have performed his experiments with balls rolling down nearly frictionless inclined planes to slow the motion and increase the timing accuracy. Increasingly precise experiments have been performed, such as those performed by Loránd Eötvös , using
15128-403: The very rare cluster decay of radium-223, one of the daughter products of natural uranium-235, and the decay chain of neptunium-237, traces of which are produced by neutron capture in uranium ores. Lead-213 also occurs in the decay chain of neptunium-237. Lead-210 is particularly useful for helping to identify the ages of samples by measuring its ratio to lead-206 (both isotopes are present in
15252-535: The weight. Robert Hooke had published his concept of gravitational forces in 1674, stating that all celestial bodies have an attraction or gravitating power towards their own centers, and also attract all the other celestial bodies that are within the sphere of their activity. He further stated that gravitational attraction increases by how much nearer the body wrought upon is to its own center. In correspondence with Isaac Newton from 1679 and 1680, Hooke conjectured that gravitational forces might decrease according to
15376-534: Was used to make sling bullets from the 5th century BC. In Roman times, lead sling bullets were amply used, and were effective at a distance of between 100 and 150 meters. The Balearic slingers , used as mercenaries in Carthaginian and Roman armies, were famous for their shooting distance and accuracy. Lead was used for making water pipes in the Roman Empire ; the Latin word for the metal, plumbum ,
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