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In chemistry, the molar mass (M) (sometimes called molecular weight or formula weight, but see related quantities for usage) of a chemical compound is defined as the ratio between the mass and the amount of substance (measured in moles) of any sample of the compound. [1] The molar mass is a bulk, not molecular, property of a substance.
Compounds with oxidation states +5 are somewhat elusive, and often found associated to an oxide (O 2−) or nitride (N 3−) ligand. [29] One example is the blue anion hypomanganate [MnO 4] 3−. [30] Mn(IV) is somewhat enigmatic because it is common in nature but far rarer in synthetic chemistry. The most common Mn ore, pyrolusite, is MnO 2.
Thirty-three artificial isotopes of zirconium have been synthesized, ranging in atomic mass from 77 to 114. [10] [17] 93 Zr is the longest-lived artificial isotope, with a half-life of 1.61×10 6 years. Radioactive isotopes at or above mass number 93 decay by electron emission, whereas those at or below 89 decay by positron emission.
Compounds of chromium(V) are rather rare; the oxidation state +5 is only realized in few compounds but are intermediates in many reactions involving oxidations by chromate. The only binary compound is the volatile chromium(V) fluoride (CrF 5). This red solid has a melting point of 30 °C and a boiling point of 117 °C.
[35] [36] Palladium is found in the rare minerals cooperite [37] and polarite. [38] Many more Pd minerals are known, but all of them are very rare. [39] Palladium is also produced in nuclear fission reactors and can be extracted from spent nuclear fuel (see synthesis of precious metals), though this source for palladium is not used.
It occurs naturally in many minerals, usually in combination with sulfur and metals, but also as a pure elemental crystal. It has various allotropes, but only the grey form, which has a metallic appearance, is important to industry. The primary use of arsenic is in alloys of lead (for example, in car batteries and ammunition).
The unusual compound Ge 6 Cl 16 has been prepared that contains the Ge 5 Cl 12 unit with a neopentane structure. [50] Germane (GeH 4) is a compound similar in structure to methane. Polygermanes—compounds that are similar to alkanes—with formula Ge n H 2n+2 containing up to five germanium atoms are known. [42]
Zinc chemistry resembles that of the late first-row transition metals, nickel and copper, [53] as well as certain main group elements. Almost all zinc compounds have the element in the +2 oxidation state. [54] When Zn 2+ compounds form, the outer shell s electrons are lost, yielding a bare zinc ion with the electronic configuration [Ar]3d 10. [55]