Question

Use Hund’s rule to derive the electronic configuration of Ce³⁺ ion, and calculate its magnetic moment on the basis of ‘spin – only’ formula.

Answer 1

The atomic number of Ce is 58. Its electronic configuration is [Xe] 4f² 5d⁰ 6s² . 

It loses three electrons (one 4f and two 6s) to form Ce³⁺ ion with electronic configuration [Xe] 4f¹ 5d⁰ 6s⁰ .The electron distribution in 4f orbital is

It contains one paired electron. 

∴ Magnetic moment μ = \(\sqrt {n(n + 2)}\) = \(\sqrt {1(1 + 2)}\) = 1.73 B.M.