Choose the ground state electron configuration for Cr3+. a) [Ar]
b) [Ar]4s23d1
c) [Ar]4s13d2
d) [Ar]4s23d6
e) [Ar]3d3

b) [Ar]4s²3d1¹

Explanation:

Chromium, Cr, is the atom with atomic number 24 (That is, 24 protons).

A Cr³⁺ contains 3 electrons less than number of protons. That is 21electrons.

The Argon, Ar, contains 18 electrons. That means the electronic configuration of Cr³⁺ contains 3 electrons more than Ar.

Following the Hund's rule, these three electrons will occupy the 4S orbital (2 electrons) and the 2d orbital (1 electron).  

Thus, right solution is: