Why is the nomenclature for Mercury (I) Fluoride Hg2F2 and not HgF?

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Why is the nomenclature for Mercury (I) Fluoride Hg2F2 and not HgF?

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Answer 1 · 2016-12-03T14:52:39

Because mercurous ion is the $H g_{2}^{2 +}$ $Hg_2^(2+)$ ion...........The empirical formula of mercurous halide may be $H g X$ $HgX$ , but its molecular formula is $H g_{2} X_{2}$ $Hg_2X_2$ .

Explanation:

And thus $mercurous halide$ $"mercurous halide"$ is $H g_{2} X_{2}$ $Hg_2X_2$ ; and $mercuric halide$ $"mercuric halide"$ is $H g X_{2}$ $HgX_2$ . As is common with $ous$ $"ous"$ versus $ic$ $"ic"$ endings, the $ic$ $"ic"$ denotes the higher oxidation state.

In $H g X_{2}$ $HgX_2$ the metal displays a formal $+ I I$ $+II$ oxidation state; in $H g_{2} X_{2}$ $Hg_2X_2$ the metal displays a formal $+ I$ $+I$ oxidation state. Where there is an $element-element bond$ $"element-element bond"$ , as here in $H g - H g$ $Hg-Hg$ , or in a $C - C$ $C-C$ linkage, the 2 electrons of the bond are assumed to be distributed EQUALLY to the bound atoms. When we assign oxidation states for $element-heteroelement bonds$ $"element-heteroelement bonds"$ , the most electronegative atom gets the 2 electrons from the bond.

And thus for $H O - C R_{3}$ $HO-CR_3$ , we get formally $H O^{-}$ $HO^(-)$ and $^{+} C R_{3}$ $""^(+)CR_3$ . The ipso carbon in $^{+} C R_{3}$ $""^(+)CR_3$ has a FORMAL $C (+ I)$ $C(+I)$ oxidation state.

I write $formal$ $"formal"$ guardedly. Of course with such designations, the assignment of oxidation number is very much a formalism, a practice with little fundamental significance, but there is utility in assigning oxidation numbers for balancing redox reactions.

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Why is the nomenclature for Mercury (I) Fluoride Hg2F2 and not HgF?

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