Question

The lathanide ion that would show colour is ______.

Options

• Gd³⁺

• Sm³⁺

• La³⁺

• Lu³⁺

Answer 1

The lathanide ion that would show colour is Sm³⁺.

Explanation:

The colour of Lanthanides elements depends in the number of unpaired electrons present in the 4f orbital. Electronic configuration of the green Lanthanides is as follows

Gd³⁺  = 4f⁷

Sm³⁺ = 4f⁵ 

La³⁺ = 4f⁰

Lu³⁺ = 4f¹⁴ 

The ion which have fully filled to orbital or absence of an electron in f orbital will not give any colour. Gd³⁺ have half filled 4f orbital which is a stable configuration. Only Sm³⁺ have partly filled 4f orbital which can easily undergoes excitation and results in the formation of colour.