The electron configuration of Cr3+ is a [Ar] 4s23d3.
The Correct Answer and Explanation is:
The electron configuration of Cr3+ is often written as [Ar] 3d³. The explanation involves understanding the behavior of chromium and its ionization.
Chromium (Cr) has an atomic number of 24, so the electron configuration of a neutral chromium atom is:
Cr: [Ar] 4s² 3d⁴
This means that in its ground state, chromium has two electrons in the 4s orbital and four electrons in the 3d orbital. However, when chromium forms a Cr³+ ion, it loses three electrons. The key to understanding this configuration lies in knowing which electrons are lost during ionization.
In the case of transition metals like chromium, the 4s electrons are lost first because they are higher in energy than the 3d electrons. When Cr loses three electrons to become Cr³+, the two 4s electrons are removed first, followed by one electron from the 3d orbital. This results in the electron configuration:
Cr³+: [Ar] 3d³
This configuration is more stable because having three unpaired 3d electrons allows for a relatively stable arrangement in a transition metal ion. In general, the loss of electrons from the 4s orbital is characteristic of transition metals when they form positive ions.
Therefore, the correct electron configuration for Cr³+ is [Ar] 3d³, not [Ar] 4s² 3d³, as the 4s electrons are removed before the 3d electrons during ionization.
