Mercury(I) hydride (systematically named mercury hydride) is an inorganic compound with the

chemical formula In chemistry, a chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbol ...

HgH. It has not yet been obtained in bulk, hence its bulk properties remain unknown. However, molecular mercury(I) hydrides with the formulae HgH and have been isolated in solid gas matrices. The molecular hydrides are very unstable toward

thermal decomposition Thermal decomposition, or thermolysis, is a chemical decomposition caused by heat. The decomposition temperature of a substance is the temperature at which the substance chemically decomposes. The reaction is usually endothermic as heat is re ...

. As such the compound is not well characterised, although many of its properties have been calculated via computational chemistry.

Molecular forms

History

In 1979 and 1985, Swiss chemical physicists, Egger and Gerber, and Soviet chemical physicists, Kolbycheva and Kolbychev, independently, theoretically determined that it is feasible to develop a mercury(I) hydride molecular laser.

Chemical properties

Mercury(I) hydride is an unstable

gas Gas is one of the four fundamental states of matter (the others being solid, liquid, and plasma). A pure gas may be made up of individual atoms (e.g. a noble gas like neon), elemental molecules made from one type of atom (e.g. oxygen), or ...

and is the heaviest group 12 monohydride. n mercury(I) hydride, the formal

oxidation state In chemistry, the oxidation state, or oxidation number, is the hypothetical charge of an atom if all of its bonds to different atoms were fully ionic. It describes the degree of oxidation (loss of electrons) of an atom in a chemical compound. C ...

s of hydrogen and mercury are −1 and +1, respectively, because of the

electronegativity Electronegativity, symbolized as , is the tendency for an atom of a given chemical element to attract shared electrons (or electron density) when forming a chemical bond. An atom's electronegativity is affected by both its atomic number and the ...

of mercury is lower than that of hydrogen. The stability of the diatomic metal hydrides with the formula MH (M = Zn-Hg) increases as the atomic number of M increases. The Hg-H bond is very weak and therefore the compound has only been

matrix isolated Matrix most commonly refers to: * ''The Matrix'' (franchise), an American media franchise ** ''The Matrix'', a 1999 science-fiction action film ** "The Matrix", a fictional setting, a virtual reality environment, within ''The Matrix'' (franchis ...

at temperatures up to 6 K. The dihydride, HgH₂, has also been detected this way. Dimercurane-3D-vdW

A related compound is dimercurane(2), or bis(hydridomercury)(''Hg''—''Hg''), with the formula , which can be considered to be dimeric mercury(I) hydride. It spontaneously decomposes into the monomeric form.

Electronic nature

The mercury centre in mercury complexes such as hydridomercury can accept or donate a single

electron The electron ( or ) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary particles because they have no ...

by association: :HgH + R → HHgR Because of this acceptance or donation of the electron, hydridomercury has radical character. It is a moderately reactive monoradical.

References

{{mercury compounds Mercury(I) compounds Metal hydrides