Question

What is the electron configuration of ${\mathrm{Cr}}^{3+}$?

Answer 1

Chromium:

• Chromium is a d-block element having atomic number 24.
• The chemical symbol of Chromium is ‘Cr’

Electronic configuration of d-block

• In general, the electronic configuration of these elements is $(\mathrm{n}-1){\mathrm{d}}^{1-10}{\mathrm{ns}}^{1-2}$.
• Here, (n–1) stands for the inner $d$orbitals which may have one to ten electrons, and the outermost $\mathrm{n}s$ orbital may have one or two electrons.

Electronic configuration of ${\mathrm{Cr}}^{3+}$

• $\mathrm{Cr}$ is an exception where the last electron enters into the 3d orbital instead of 4s orbital to attain half-filled stability.
• The electronic configuration of chromium is $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^{2}3{\mathrm{p}}^{6}4{\mathrm{s}}^{1}3{\mathrm{d}}^5$.
• ${\mathrm{Cr}}^{3+}$ is formed by losing three electrons from the neutral chromium atom.
• So, the electronic configuration of ${\mathrm{Cr}}^{3+}$ is $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^{2}3{\mathrm{p}}^{6}3{\mathrm{d}}^3$.