Question #1e11d

1 Answer
Aug 21, 2017

Answer:

Here's how I see it.

Explanation:

We can think of the #"HgI"_3^"-"# as being formed by the reaction

#"Hg"^"2+" + 3"I"^"-" → "HgI"_3^"-"#

The electron configuration of a neutral #"Hg"# atom is

#"Hg"^0 = "[Xe] 6s"^2 "4f"^14 "5d"^10#

For #"Hg"^"2+"#, the electron configuration is

#"Hg"^"2+" = "[Xe] 4f"^14 "5d"^10#

The #"Hg"^"2+"# ion, however, has vacant #"6s"# and #"6p"# orbitals.

It can hybridize a #"6s"# and two of the #"6p"# orbitals to form three new vacant #"sp"^3# hybrid orbitals.

These can each overlap with a filled #"5p"# orbital of an iodide ion.

Thus, the new ion is trigonal planar, and the #"Hg-I"# bonds are coordinate covalent bonds in which the iodide ions are contributing both electrons of the covalent bond.