Question

Correct electronic configuration of Co${}^{+2}$ ion is:

• A. [Ar] 4s${}^2$ 3d${}^5$
• B. [Ar] 3d${}^7$
• C. [Ar]4s${}^1$ 3d${}^6$
• D. [Ar] 4s${}^2$ 3d${}^7$

Answer 1

Answer: (B)

[Ar] 3d${}^7$

Atomic number of Cobalt = 27
Electronic configuration of Co is $\left[Ar\right]3d^{7}4s^2$
It loses two electrons from 4s orbital to form $C{O}^{+2}$ ion.
Electronic configuration of $C{o}^{+2}$ is $\left[Ar\right]3d^7$