Question

14 mark for review
which of the following represents the ground state electron configuration for the mn³+ ion? (atomic number mn = 25)
a 1s²2s²2p⁶3s²3p⁶3d⁴
b 1s²2s²2p⁶3s²3p⁶3d⁵4s²
c 1s²2s²2p⁶3s²3p⁶3d²4s²
d 1s²2s²2p⁶3s²3p⁶3d⁸4s²

Explanation:

Step1: Determine the electron configuration of Mn atom

The atomic number of Mn is 25. The electron configuration of Mn atom is \(1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}3d^{5}4s^{2}\) (using the Aufbau principle, Pauli exclusion principle and Hund's rule).

Step2: Remove electrons to form \(Mn^{3 +}\) ion

When forming \(Mn^{3+}\) ion, we remove 3 electrons. We first remove electrons from the highest - energy orbital. The order of electron removal is from the \(4s\) orbital first (since for transition metals, when forming cations, electrons are removed from the \(ns\) orbital before the \((n - 1)d\) orbital). We remove 2 electrons from the \(4s\) orbital and 1 electron from the \(3d\) orbital.
The electron configuration of \(Mn^{3+}\) is \(1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}3d^{4}\)

Answer:

A. \(1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}3d^{4}\)