Chemical Forums
Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: Win,odd Dhamnekar on July 07, 2021, 03:21:05 AM
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Hello,
I am not a graduate in chemistry. Hence I prefer to post all my questions under this forum with obviously some exceptions.
1) Why does the chemistry professional prefer to draw Lewis dot structure of Hg2Br2 Mercury Bromide as given in figure b)? Why is Lewis dot structure drawn in a) wrong?
2)Following is the dissociation equation and Ksp expression for Mercury Bromide Hg2Br2 ::equil:: Hg22+ (aq)+ 2Br- (aq) Ksp=[Hg22+] [Br-]2
Note how the mercury(I) ion is written. Hg22+ is correct.(why?) Do not write it as 2Hg+.(why?) Writing [Hg+]2 in the Ksp expression is wrong.(why?)
Mercury have two valence electrons in 6s orbital, Bromine have 7 valence electrons in 4s, 4p orbitals.
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Structure a is correct. Mercury(I) bromide exists as Hg2Br2. Monomeric HgBr doesn't exist, except perhaps as a short-lived reactive species in the gas phase. In what context did this "chemistry professional" give structure b?
The dissociation equation you give for Hg2Br2 is correct (assuming Br2- is simply a typo for Br-). The mercury ion exists as Hg22+, not Hg+. If you're asking why that is the case, I'm not certain. Hg+ will have an unpaired 6s electron that can potentially form bonds, which is not the case for ions like Na+ or Cu+.
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Wolfram alpha Lewis dot structure widget gave me following molecular structure for Hg2Br2 as given in b). But you said figure a) is correct. What is your explanation for this contradiction?
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https://en.wikipedia.org/wiki/Mercury(I)_chloride
https://en.wikipedia.org/wiki/Mercury_polycations
The presence of the Hg22+ ion in solution was shown by Ogg in 1898. In 1900, Baker showed the presence of HgCl dimers in the vapour phase. The presence of Hg22+ units in the solid state was first determined in 1926 using X-ray diffraction.