Question

what is the (ground state) electron configuration of fe^{3+}?
a. ar4s^{2} 3d^{6}
b. ar4s^{2} 3d^{3}
c. ar 4s^{2} 3d^{9}
ar 3d^{5}

Explanation:

Step1: Determine the electron configuration of Fe atom

The atomic number of Fe is 26. The electron configuration of Fe atom is \([Ar]4s^{2}3d^{6}\).

Step2: Consider the formation of \(Fe^{3 +}\) ion

When \(Fe\) forms \(Fe^{3+}\) ion, it loses 3 electrons. Electrons are lost first from the \(4s\) orbital (since \(4s\) has higher energy than \(3d\) when it is occupied). So, we lose 2 electrons from \(4s\) and 1 electron from \(3d\).

Answer:

D. \([Ar]3d^{5}\)