Question

The quantum number which explains the line spectra observed as doublets in case of hydrogen and alkali metals and doublets and triplets in case of alkaline earth metals is :

• A. spin
• B. azimuthal
• C. magnetic
• D. principal

Answer 1

The correct option is A spin

A doublet is a quantum state of a system with a spin of $1/2$, such that there are two allowed values of the spin component, $-1/2$ and $+1/2$. In the same way, the triplet is also explained by the spin quantum number.
The quantum number which explains the line spectra observed as doublets in case of hydrogen and alkali metals and doublets and triplets in case of alkaline earth metals is the spin quantum number.