Question

A `M^(2+)` ion derived from a metal in the first transition metal series has four electrons in `3d` subshell. What element might `M` be?

Answer 1

Correct Answer - Chromium
`{:(,"Electron configuration of "M^(2+)is:,,[Ar]^(18)4s^(@)3d^(4)),( :.,"Electron configuration of"M is:,,[Ar]^(18)4s^(1)3d^(5)("and not" 5s^(2)3d^(4))):}`
So total number of electrons `= 24`.
Hence, metal `M` is chromium `(Cr)`.