How many unpaired electrons would you expect for the complex ion: [Cr(CN)₆]^4-? A) 0 B) 5 C) 3 D) 1 E) 2

Question

Quizplus · Accepted Answer

The complex ion has a coordination number of 6 (the Cr ion is surrounded by 6 ligands), and the electron configuration of Cr is [Ar] 3d54s1. When the Cr ion bonds with the six CN- ligands, the 4s and three of the 4d electrons are used up, leaving two 4d electrons unpaired. When the ion bonds with the two S2- ligands, one of the unpaired d electrons is paired up, leaving one unpaired electron. Therefore, the total number of unpaired electrons in the complex ion is 2+1=3. The correct answer is therefore (C) 3.

How Many Unpaired Electrons Would You Expect for the Complex