Mudstone , a type of mudrock , is a fine-grained sedimentary rock whose original constituents were clays or muds . Mudstone is distinguished from shale by its lack of fissility .
80-406: The term mudstone is also used to describe carbonate rocks ( limestone or dolomite ) that are composed predominantly of carbonate mud. However, in most contexts, the term refers to siliciclastic mudstone, composed mostly of silicate minerals. The NASA Curiosity rover has found deposits of mudstone on Mars that contain organic substances such as propane , benzene and toluene . There
160-409: A buffer to stabilise it in the range 7.37–7.43: Exhaled CO 2 (g) depletes CO 2 (aq) , which in turn consumes H 2 CO 3 , causing the equilibrium of the first reaction to try to restore the level of carbonic acid by reacting bicarbonate with a hydrogen ion, an example of Le Châtelier's principle . The result is to make the blood more alkaline (raise pH). By the same principle, when
240-403: A base. This is also true of some compounds with ionic character, typically oxides or hydroxides of less-electropositive metals (so the compound also has significant covalent character), such as zinc oxide , aluminium hydroxide , aluminium oxide and lead(II) oxide . Electrostatic forces between particles are strongest when the charges are high, and the distance between the nuclei of the ions
320-679: A compound with no net electric charge (electrically neutral). The constituent ions are held together by electrostatic forces termed ionic bonds . The component ions in a salt can be either inorganic , such as chloride (Cl ), or organic , such as acetate ( CH 3 COO ). Each ion can be either monatomic (termed simple ion ), such as sodium (Na ) and chloride (Cl ) in sodium chloride , or polyatomic , such as ammonium ( NH 4 ) and carbonate ( CO 3 ) ions in ammonium carbonate . Salts containing basic ions hydroxide (OH ) or oxide (O ) are classified as bases , for example sodium hydroxide . Individual ions within
400-660: A further increase to the upper limit for the matrix size in order to bring it into line with the upper limit for silt (63 μm). On December 13, 2016, NASA reported further evidence supporting habitability on the planet Mars as the Curiosity rover climbed higher, studying younger layers, on Mount Sharp . Also reported, the very soluble element boron was detected for the first time on Mars. In June 2018 , NASA reported that Curiosity had detected kerogen and other complex organic compounds from mudstone rocks approximately 3.5 billion years old. Carbonate A carbonate
480-587: A model with fractional bonds and delocalized charges: Metal carbonates generally decompose on heating, liberating carbon dioxide leaving behind an oxide of the metal. This process is called calcination , after calx , the Latin name of quicklime or calcium oxide , CaO, which is obtained by roasting limestone in a lime kiln : As illustrated by its affinity for Ca , carbonate is a ligand for many metal cations. Transition metal carbonate and bicarbonate complexes feature metal ions covalently bonded to carbonate in
560-415: A network with long-range crystalline order. Many other inorganic compounds were also found to have similar structural features. These compounds were soon described as being constituted of ions rather than neutral atoms , but proof of this hypothesis was not found until the mid-1920s, when X-ray reflection experiments (which detect the density of electrons), were performed. Principal contributors to
640-453: A paste and then heated to a temperature where the ions in neighboring reactants can diffuse together during the time the reactant mixture remains in the oven. Other synthetic routes use a solid precursor with the correct stoichiometric ratio of non-volatile ions, which is heated to drive off other species. In some reactions between highly reactive metals (usually from Group 1 or Group 2 ) and highly electronegative halogen gases, or water,
720-416: A potential energy well with minimum energy when the nuclei are separated by a specific equilibrium distance. If the electronic structure of the two interacting bodies is affected by the presence of one another, covalent interactions (non-ionic) also contribute to the overall energy of the compound formed. Salts are rarely purely ionic, i.e. held together only by electrostatic forces. The bonds between even
800-400: A reducing agent such as carbon) such that the metal ions gain electrons to become neutral atoms. According to the nomenclature recommended by IUPAC , salts are named according to their composition, not their structure. In the most simple case of a binary salt with no possible ambiguity about the charges and thus the stoichiometry , the common name is written using two words. The name of
880-529: A role in determining the strength of the interactions and propensity to melt. Even when the local structure and bonding of an ionic solid is disrupted sufficiently to melt it, there are still strong long-range electrostatic forces of attraction holding the liquid together and preventing ions boiling to form a gas phase. This means that even room temperature ionic liquids have low vapour pressures, and require substantially higher temperatures to boil. Boiling points exhibit similar trends to melting points in terms of
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#1732790887640960-460: A salt usually have multiple near neighbours, so they are not considered to be part of molecules, but instead part of a continuous three-dimensional network. Salts usually form crystalline structures when solid. Salts composed of small ions typically have high melting and boiling points , and are hard and brittle . As solids they are almost always electrically insulating , but when melted or dissolved they become highly conductive , because
1040-498: A shorter wavelength when they are involved in more covalent interactions. This occurs during hydration of metal ions, so colorless anhydrous salts with an anion absorbing in the infrared can become colorful in solution. Salts exist in many different colors , which arise either from their constituent anions, cations or solvates . For example: Some minerals are salts, some of which are soluble in water. Similarly, inorganic pigments tend not to be salts, because insolubility
1120-487: A variety of accessory minerals . In the Dunham classification (Dunham, 1962) system of limestones , a mudstone is defined as a mud-supported carbonate rock that contains less than 10% grains. Most recently, this definition has been clarified as a matrix-supported carbonate-dominated rock composed of more than 90% carbonate mud (<63 μm) component . A recent study by Lokier and Al Junaibi (2016) has highlighted that
1200-406: A variety of bonding modes. Lithium , sodium , potassium , rubidium , caesium , and ammonium carbonates are water-soluble salts, but carbonates of 2+ and 3+ ions are often poorly soluble in water. Of the insoluble metal carbonates, CaCO 3 is important because, in the form of scale , it accumulates in and impedes flow through pipes. Hard water is rich in this material, giving rise to
1280-527: A variety of structures are commonly observed, and theoretically rationalized by Pauling's rules . In some cases, the anions take on a simple cubic packing and the resulting common structures observed are: Some ionic liquids , particularly with mixtures of anions or cations, can be cooled rapidly enough that there is not enough time for crystal nucleation to occur, so an ionic glass is formed (with no long-range order). Within any crystal, there will usually be some defects. To maintain electroneutrality of
1360-626: A wide variety of uses and applications. Many minerals are ionic. Humans have processed common salt (sodium chloride) for over 8000 years, using it first as a food seasoning and preservative, and now also in manufacturing, agriculture , water conditioning, for de-icing roads, and many other uses. Many salts are so widely used in society that they go by common names unrelated to their chemical identity. Examples of this include borax , calomel , milk of magnesia , muriatic acid , oil of vitriol , saltpeter , and slaked lime . Soluble salts can easily be dissolved to provide electrolyte solutions. This
1440-483: Is K). When one of the ions already has a multiplicative prefix within its name, the alternate multiplicative prefixes ( bis- , tris- , tetrakis- , ...) are used. For example, Ba(BrF 4 ) 2 is named barium bis(tetrafluoridobromate) . Compounds containing one or more elements which can exist in a variety of charge/ oxidation states will have a stoichiometry that depends on which oxidation states are present, to ensure overall neutrality. This can be indicated in
1520-532: Is a salt of carbonic acid , ( H 2 CO 3 ), characterized by the presence of the carbonate ion , a polyatomic ion with the formula CO 2− 3 . The word "carbonate" may also refer to a carbonate ester , an organic compound containing the carbonate group O=C(−O−) 2 . The term is also used as a verb, to describe carbonation : the process of raising the concentrations of carbonate and bicarbonate ions in water to produce carbonated water and other carbonated beverages – either by
1600-407: Is a simple way to control the concentration and ionic strength . The concentration of solutes affects many colligative properties , including increasing the osmotic pressure , and causing freezing-point depression and boiling-point elevation . Because the solutes are charged ions they also increase the electrical conductivity of the solution. The increased ionic strength reduces the thickness of
1680-408: Is clay particles. Another definition is that mudstone is a sedimentary rock in which neither silt, clay, nor coarser grains is predominant. Rock of this composition that does show laminations or fissility is sometimes described as mudshale rather than mudstone . The lack of fissility or layering in mudstone may be due to either original texture or the disruption of layering by burrowing organisms in
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#17327908876401760-402: Is double bonded. These compounds are also known as organocarbonates or carbonate esters, and have the general formula R−O−C(=O)−O−R′ , or RR′CO 3 . Important organocarbonates include dimethyl carbonate , the cyclic compounds ethylene carbonate and propylene carbonate , and the phosgene replacement, triphosgene . Three reversible reactions control the pH balance of blood and act as
1840-400: Is highest in polar solvents (such as water ) or ionic liquids , but tends to be low in nonpolar solvents (such as petrol / gasoline ). This contrast is principally because the resulting ion–dipole interactions are significantly stronger than ion-induced dipole interactions, so the heat of solution is higher. When the oppositely charged ions in the solid ionic lattice are surrounded by
1920-535: Is named iron(2+) sulfate (with the 2+ charge on the Fe ions balancing the 2− charge on the sulfate ion), whereas Fe 2 (SO 4 ) 3 is named iron(3+) sulfate (because the two iron ions in each formula unit each have a charge of 3+, to balance the 2− on each of the three sulfate ions). Stock nomenclature , still in common use, writes the oxidation number in Roman numerals (... , −II, −I, 0, I, II, ...). So
2000-552: Is not a single definition of mudstone that has gained general acceptance, though there is wide agreement that mudstones are fine-grained sedimentary rocks, composed mostly of silicate grains with a grain size less than 0.063 millimetres (0.0025 in). Individual grains this size are too small to be distinguished without a microscope, which means that most classifications emphasize texture rather than mineral composition, and mudstones have historically received less attention from petrologists than have sandstones . The simplest definition
2080-441: Is related to the disparate lattice energies of solids composed of mono- vs dianions, as well as mono- vs dications. In aqueous solution , carbonate, bicarbonate, carbon dioxide, and carbonic acid participate in a dynamic equilibrium . In strongly basic conditions, the carbonate ion predominates, while in weakly basic conditions, the bicarbonate ion is prevalent. In more acid conditions, aqueous carbon dioxide , CO 2 (aq) ,
2160-548: Is required for fastness. Some organic dyes are salts, but they are virtually insoluble in water. Salts can elicit all five basic tastes , e.g., salty ( sodium chloride ), sweet ( lead diacetate , which will cause lead poisoning if ingested), sour ( potassium bitartrate ), bitter ( magnesium sulfate ), and umami or savory ( monosodium glutamate ). Salts of strong acids and strong bases (" strong salts ") are non- volatile and often odorless, whereas salts of either weak acids or weak bases (" weak salts ") may smell like
2240-414: Is small. In such cases, the compounds generally have very high melting and boiling points and a low vapour pressure . Trends in melting points can be even better explained when the structure and ionic size ratio is taken into account. Above their melting point, salts melt and become molten salts (although some salts such as aluminium chloride and iron(III) chloride show molecule-like structures in
2320-419: Is that a mudstone is a fine-grained clastic sedimentary rock that is not laminated or fissile . Most definitions also include a requirement that the rock contain significant amounts of both silt- and clay-sized grains. One common requirement is that a mudstone is a mudrock (a rock containing more than 50% silt- to clay-sized particles) in which between a third and two-thirds of the mud (silt and clay) fraction
2400-551: Is the formation of an F-center , a free electron occupying an anion vacancy. When the compound has three or more ionic components, even more defect types are possible. All of these point defects can be generated via thermal vibrations and have an equilibrium concentration. Because they are energetically costly but entropically beneficial, they occur in greater concentration at higher temperatures. Once generated, these pairs of defects can diffuse mostly independently of one another, by hopping between lattice sites. This defect mobility
2480-444: Is the main form, which, with water, H 2 O , is in equilibrium with carbonic acid – the equilibrium lies strongly towards carbon dioxide. Thus sodium carbonate is basic, sodium bicarbonate is weakly basic, while carbon dioxide itself is a weak acid. In organic chemistry a carbonate can also refer to a functional group within a larger molecule that contains a carbon atom bound to three oxygen atoms, one of which
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2560-453: Is the simplest oxocarbon anion . It consists of one carbon atom surrounded by three oxygen atoms, in a trigonal planar arrangement, with D 3h molecular symmetry . It has a molecular mass of 60.01 g/mol and carries a total formal charge of −2. It is the conjugate base of the hydrogencarbonate (bicarbonate) ion, HCO − 3 , which is the conjugate base of H 2 CO 3 , carbonic acid . The Lewis structure of
2640-421: Is the source of most transport phenomena within an ionic crystal, including diffusion and solid state ionic conductivity . When vacancies collide with interstitials (Frenkel), they can recombine and annihilate one another. Similarly, vacancies are removed when they reach the surface of the crystal (Schottky). Defects in the crystal structure generally expand the lattice parameters , reducing the overall density of
2720-411: Is the summation of the interaction of all sites with all other sites. For unpolarizable spherical ions, only the charges and distances are required to determine the electrostatic interaction energy. For any particular ideal crystal structure, all distances are geometrically related to the smallest internuclear distance. So for each possible crystal structure, the total electrostatic energy can be related to
2800-482: The Kapustinskii equation . Using an even simpler approximation of the ions as impenetrable hard spheres, the arrangement of anions in these systems are often related to close-packed arrangements of spheres, with the cations occupying tetrahedral or octahedral interstices . Depending on the stoichiometry of the salt, and the coordination (principally determined by the radius ratio ) of cations and anions,
2880-416: The anhydrous material. Molten salts will solidify on cooling to below their freezing point . This is sometimes used for the solid-state synthesis of complex salts from solid reactants, which are first melted together. In other cases, the solid reactants do not need to be melted, but instead can react through a solid-state reaction route . In this method, the reactants are repeatedly finely ground into
2960-405: The conjugate acid (e.g., acetates like acetic acid ( vinegar ) and cyanides like hydrogen cyanide ( almonds )) or the conjugate base (e.g., ammonium salts like ammonia ) of the component ions. That slow, partial decomposition is usually accelerated by the presence of water, since hydrolysis is the other half of the reversible reaction equation of formation of weak salts. Salts have long had
3040-580: The electrical double layer around colloidal particles, and therefore the stability of emulsions and suspensions . The chemical identity of the ions added is also important in many uses. For example, fluoride containing compounds are dissolved to supply fluoride ions for water fluoridation . Solid salts have long been used as paint pigments, and are resistant to organic solvents, but are sensitive to acidity or basicity. Since 1801 pyrotechnicians have described and widely used metal-containing salts as sources of colour in fireworks. Under intense heat,
3120-435: The electronegative halogens gases to salts. Salts form upon evaporation of their solutions . Once the solution is supersaturated and the solid compound nucleates. This process occurs widely in nature and is the means of formation of the evaporite minerals. Insoluble salts can be precipitated by mixing two solutions, one with the cation and one with the anion in it. Because all solutions are electrically neutral,
3200-512: The addition of carbon dioxide gas under pressure or by dissolving carbonate or bicarbonate salts into the water. In geology and mineralogy , the term "carbonate" can refer both to carbonate minerals and carbonate rock (which is made of chiefly carbonate minerals), and both are dominated by the carbonate ion, CO 2− 3 . Carbonate minerals are extremely varied and ubiquitous in chemically precipitated sedimentary rock . The most common are calcite or calcium carbonate , CaCO 3 ,
3280-658: The anion and cation. This difference in electronegativities means that the charge separation, and resulting dipole moment, is maintained even when the ions are in contact (the excess electrons on the anions are not transferred or polarized to neutralize the cations). Although chemists classify idealized bond types as being ionic or covalent, the existence of additional types such as hydrogen bonds and metallic bonds , for example, has led some philosophers of science to suggest that alternative approaches to understanding bonding are required. This could be by applying quantum mechanics to calculate binding energies. The lattice energy
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3360-511: The anions and net positive charge of the cations. There is also a small additional attractive force from van der Waals interactions which contributes only around 1–2% of the cohesive energy for small ions. When a pair of ions comes close enough for their outer electron shells (most simple ions have closed shells ) to overlap, a short-ranged repulsive force occurs, due to the Pauli exclusion principle . The balance between these forces leads to
3440-462: The atoms can be ionized by electron transfer , a process thermodynamically understood using the Born–Haber cycle . Salts are formed by salt-forming reactions Ions in salts are primarily held together by the electrostatic forces between the charge distribution of these bodies, and in particular, the ionic bond resulting from the long-ranged Coulomb attraction between the net negative charge of
3520-459: The carbonate ion has two (long) single bonds to negative oxygen atoms, and one short double bond to a neutral oxygen atom. This structure is incompatible with the observed symmetry of the ion, which implies that the three bonds are the same length and that the three oxygen atoms are equivalent. As in the case of the isoelectronic nitrate ion, the symmetry can be achieved by a resonance among three structures: This resonance can be summarized by
3600-590: The cation (the unmodified element name for monatomic cations) comes first, followed by the name of the anion. For example, MgCl 2 is named magnesium chloride , and Na 2 SO 4 is named sodium sulfate ( SO 4 , sulfate , is an example of a polyatomic ion ). To obtain the empirical formula from these names, the stoichiometry can be deduced from the charges on the ions, and the requirement of overall charge neutrality. If there are multiple different cations and/or anions, multiplicative prefixes ( di- , tri- , tetra- , ...) are often required to indicate
3680-453: The chief constituent of limestone (as well as the main component of mollusc shells and coral skeletons); dolomite , a calcium-magnesium carbonate CaMg(CO 3 ) 2 ; and siderite , or iron(II) carbonate , FeCO 3 , an important iron ore . Sodium carbonate ("soda" or "natron"), Na 2 CO 3 , and potassium carbonate ("potash"), K 2 CO 3 , have been used since antiquity for cleaning and preservation, as well as for
3760-558: The compound is the result of a reaction between a strong acid and a weak base , the result is an acid salt . If it is the result of a reaction between a strong base and a weak acid , the result is a base salt . If it is the result of a reaction between a strong acid and a strong base, the result is a neutral salt. Weak acids reacted with weak bases can produce ionic compounds with both the conjugate base ion and conjugate acid ion, such as ammonium acetate . Some ions are classed as amphoteric , being able to react with either an acid or
3840-462: The constituent ions, or the hydrated form of the same compound. The anions in compounds with bonds with the most ionic character tend to be colorless (with an absorption band in the ultraviolet part of the spectrum). In compounds with less ionic character, their color deepens through yellow, orange, red, and black (as the absorption band shifts to longer wavelengths into the visible spectrum). The absorption band of simple cations shifts toward
3920-406: The counterions can be chosen to ensure that even when combined into a single solution they will remain soluble as spectator ions . If the solvent is water in either the evaporation or precipitation method of formation, in many cases the ionic crystal formed also includes water of crystallization , so the product is known as a hydrate , and can have very different chemical properties compared to
4000-861: The crystal. Defects also result in ions in distinctly different local environments, which causes them to experience a different crystal-field symmetry , especially in the case of different cations exchanging lattice sites. This results in a different splitting of d-electron orbitals , so that the optical absorption (and hence colour) can change with defect concentration. Ionic compounds containing hydrogen ions (H ) are classified as acids , and those containing electropositive cations and basic anions ions hydroxide (OH ) or oxide (O ) are classified as bases . Other ionic compounds are known as salts and can be formed by acid–base reactions . Salts that produce hydroxide ions when dissolved in water are called alkali salts , and salts that produce hydrogen ions when dissolved in water are called acid salts . If
4080-464: The crystals, defects that involve loss of a cation will be associated with loss of an anion, i.e. these defects come in pairs. Frenkel defects consist of a cation vacancy paired with a cation interstitial and can be generated anywhere in the bulk of the crystal, occurring most commonly in compounds with a low coordination number and cations that are much smaller than the anions. Schottky defects consist of one vacancy of each type, and are generated at
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#17327908876404160-483: The development of a theoretical treatment of ionic crystal structures were Max Born , Fritz Haber , Alfred Landé , Erwin Madelung , Paul Peter Ewald , and Kazimierz Fajans . Born predicted crystal energies based on the assumption of ionic constituents, which showed good correspondence to thermochemical measurements, further supporting the assumption. Many metals such as the alkali metals react directly with
4240-521: The electrons in the metal ions or small molecules can be excited. These electrons later return to lower energy states, and release light with a colour spectrum characteristic of the species present. In chemical synthesis , salts are often used as precursors for high-temperature solid-state synthesis. Many metals are geologically most abundant as salts within ores . To obtain the elemental materials, these ores are processed by smelting or electrolysis , in which redox reactions occur (often with
4320-569: The electrostatic energy of unit charges at the nearest neighboring distance by a multiplicative constant called the Madelung constant that can be efficiently computed using an Ewald sum . When a reasonable form is assumed for the additional repulsive energy, the total lattice energy can be modelled using the Born–Landé equation , the Born–Mayer equation , or in the absence of structural information,
4400-502: The examples given above would be named iron(II) sulfate and iron(III) sulfate respectively. For simple ions the ionic charge and the oxidation number are identical, but for polyatomic ions they often differ. For example, the uranyl(2+) ion, UO 2 , has uranium in an oxidation state of +6, so would be called a dioxouranium(VI) ion in Stock nomenclature. An even older naming system for metal cations, also still widely used, appended
4480-445: The ions become completely mobile. For this reason, molten salts and solutions containing dissolved salts (e.g., sodium chloride in water) can be used as electrolytes . This conductivity gain upon dissolving or melting is sometimes used as a defining characteristic of salts. In some unusual salts: fast-ion conductors , and ionic glasses , one or more of the ionic components has a significant mobility, allowing conductivity even while
4560-469: The ions become mobile. Some salts have large cations, large anions, or both. In terms of their properties, such species often are more similar to organic compounds. In 1913 the structure of sodium chloride was determined by William Henry Bragg and William Lawrence Bragg . This revealed that there were six equidistant nearest-neighbours for each atom, demonstrating that the constituents were not arranged in molecules or finite aggregates, but instead as
4640-446: The liquid phase). Inorganic compounds with simple ions typically have small ions, and thus have high melting points, so are solids at room temperature. Some substances with larger ions, however, have a melting point below or near room temperature (often defined as up to 100 °C), and are termed ionic liquids . Ions in ionic liquids often have uneven charge distributions, or bulky substituents like hydrocarbon chains, which also play
4720-473: The long-term carbon cycle, due to the large number of marine organisms (especially coral) which are made of calcium carbonate. Increased solubility of carbonate through increased temperatures results in lower production of marine calcite and increased concentration of atmospheric carbon dioxide. This, in turn, increases Earth temperature. The amount of CO 2− 3 available is on a geological scale and substantial quantities may eventually be redissolved into
4800-435: The manufacture of glass . Carbonates are widely used in industry, such as in iron smelting, as a raw material for Portland cement and lime manufacture, in the composition of ceramic glazes , and more. New applications of alkali metal carbonates include: thermal energy storage, catalysis and electrolyte both in fuel cell technology as well as in electrosynthesis of H 2 O 2 in aqueous media. The carbonate ion
4880-399: The material as a whole remains solid. This is often highly temperature dependent, and may be the result of either a phase change or a high defect concentration. These materials are used in all solid-state supercapacitors , batteries , and fuel cells , and in various kinds of chemical sensors . The colour of a salt is often different from the colour of an aqueous solution containing
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#17327908876404960-427: The most electronegative / electropositive pairs such as those in caesium fluoride exhibit a small degree of covalency . Conversely, covalent bonds between unlike atoms often exhibit some charge separation and can be considered to have a partial ionic character. The circumstances under which a compound will have ionic or covalent character can typically be understood using Fajans' rules , which use only charges and
5040-451: The most common problems encountered when describing a mudstone is to incorrectly estimate the volume of 'grains' in the sample - in consequence, misidentifying mudstone as wackestone and vice versa. The original Dunham classification (1962) defined the matrix as clay and fine-silt size sediment <20 μm in diameter. This definition was redefined by Embry & Klovan (1971) to a grain size of less than or equal to 30 μm. Wright (1992) proposed
5120-440: The name by specifying either the oxidation state of the elements present, or the charge on the ions. Because of the risk of ambiguity in allocating oxidation states, IUPAC prefers direct indication of the ionic charge numbers. These are written as an arabic integer followed by the sign (... , 2−, 1−, 1+, 2+, ...) in parentheses directly after the name of the cation (without a space separating them). For example, FeSO 4
5200-412: The need for infrastructural water softening . Acidification of carbonates generally liberates carbon dioxide : Thus, scale can be removed with acid. In solution the equilibrium between carbonate, bicarbonate, carbon dioxide and carbonic acid is sensitive to pH, temperature, and pressure. Although di- and trivalent carbonates have low solubility, bicarbonate salts are far more soluble. This difference
5280-444: The observations. Small amounts of carbonate deposits have been found on Mars via spectral imaging and Martian meteorites also contain small amounts. Groundwater may have existed at Gusev and Meridiani Planum . Salt (chemistry) In chemistry , a salt or ionic compound is a chemical compound consisting of an assembly of positively charged ions ( cations ) and negatively charged ions ( anions ), which results in
5360-467: The opposite pole of a polar molecule, the solid ions are pulled out of the lattice and into the liquid. If the solvation energy exceeds the lattice energy , the negative net enthalpy change of solution provides a thermodynamic drive to remove ions from their positions in the crystal and dissolve in the liquid. In addition, the entropy change of solution is usually positive for most solid solutes like salts, which means that their solubility increases when
5440-410: The pH is too high, the kidneys excrete bicarbonate ( HCO − 3 ) into urine as urea via the urea cycle (or Krebs–Henseleit ornithine cycle). By removing the bicarbonate, more H is generated from carbonic acid ( H 2 CO 3 ), which comes from CO 2 (g) produced by cellular respiration . Crucially, a similar buffer operates in the oceans. It is a major factor in climate change and
5520-407: The relative compositions, and cations then anions are listed in alphabetical order. For example, KMgCl 3 is named magnesium potassium trichloride to distinguish it from K 2 MgCl 4 , magnesium dipotassium tetrachloride (note that in both the empirical formula and the written name, the cations appear in alphabetical order, but the order varies between them because the symbol for potassium
5600-412: The sea and released to the atmosphere, increasing CO 2 levels even more. It is generally thought that the presence of carbonates in rock is strong evidence for the presence of liquid water. Recent observations of the planetary nebula NGC 6302 show evidence for carbonates in space, where aqueous alteration similar to that on Earth is unlikely. Other minerals have been proposed which would fit
5680-485: The sediment prior to lithification . Mudstone looks like hardened clay and, depending upon the circumstances under which it was formed, it may show cracks or fissures, like a sun-baked clay deposit. When the mineral composition of mudstones has been determined, using such techniques as scanning electron microscopy , electron probe microanalysis , or X-ray diffraction analysis , they have been found to be composed primarily of clay minerals , quartz , and feldspars , with
5760-448: The size of ions and strength of other interactions. When vapourized, the ions are still not freed of one another. For example, in the vapour phase sodium chloride exists as diatomic "molecules". Most salts are very brittle . Once they reach the limit of their strength, they cannot deform malleably , because the strict alignment of positive and negative ions must be maintained. Instead the material undergoes fracture via cleavage . As
5840-418: The sizes of each ion. According to these rules, compounds with the most ionic character will have large positive ions with a low charge, bonded to a small negative ion with a high charge. More generally HSAB theory can be applied, whereby the compounds with the most ionic character are those consisting of hard acids and hard bases: small, highly charged ions with a high difference in electronegativities between
5920-420: The sodium chloride structure (coordination number 6), and less again than those with a coordination number of 4. When simple salts dissolve , they dissociate into individual ions, which are solvated and dispersed throughout the resulting solution. Salts do not exist in solution. In contrast, molecular compounds, which includes most organic compounds, remain intact in solution. The solubility of salts
6000-790: The solvent, so certain patterns become apparent. For example, salts of sodium , potassium and ammonium are usually soluble in water. Notable exceptions include ammonium hexachloroplatinate and potassium cobaltinitrite . Most nitrates and many sulfates are water-soluble. Exceptions include barium sulfate , calcium sulfate (sparingly soluble), and lead(II) sulfate , where the 2+/2− pairing leads to high lattice energies. For similar reasons, most metal carbonates are not soluble in water. Some soluble carbonate salts are: sodium carbonate , potassium carbonate and ammonium carbonate . Salts are characteristically insulators . Although they contain charged atoms or clusters, these materials do not typically conduct electricity to any significant extent when
6080-403: The substance is solid. In order to conduct, the charged particles must be mobile rather than stationary in a crystal lattice . This is achieved to some degree at high temperatures when the defect concentration increases the ionic mobility and solid state ionic conductivity is observed. When the salts are dissolved in a liquid or are melted into a liquid , they can conduct electricity because
6160-422: The surfaces of a crystal, occurring most commonly in compounds with a high coordination number and when the anions and cations are of similar size. If the cations have multiple possible oxidation states , then it is possible for cation vacancies to compensate for electron deficiencies on cation sites with higher oxidation numbers, resulting in a non-stoichiometric compound . Another non-stoichiometric possibility
6240-399: The temperature increases. There are some unusual salts such as cerium(III) sulfate , where this entropy change is negative, due to extra order induced in the water upon solution, and the solubility decreases with temperature. The lattice energy , the cohesive forces between these ions within a solid, determines the solubility. The solubility is dependent on how well each ion interacts with
6320-413: The temperature is elevated (usually close to the melting point) a ductile–brittle transition occurs, and plastic flow becomes possible by the motion of dislocations . The compressibility of a salt is strongly determined by its structure, and in particular the coordination number . For example, halides with the caesium chloride structure (coordination number 8) are less compressible than those with
6400-413: The two solutions mixed must also contain counterions of the opposite charges. To ensure that these do not contaminate the precipitated salt, it is important to ensure they do not also precipitate. If the two solutions have hydrogen ions and hydroxide ions as the counterions, they will react with one another in what is called an acid–base reaction or a neutralization reaction to form water. Alternately
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