Question

Among the following allotropic forms of sulphur, the number of allotropic forms, which will show paramagnetism is __________

Hint:

$S_2$ is the sulfur analogue of $O_2$. If $O_2$ is paramagnetic due to MOT, $S_2$ will be too!

Answer 1

Correct Answer: 1

Step 1: $\alpha$-Sulphur (Rhombic) and $\beta$-Sulphur (Monoclinic) consist of $S_8$ puckered rings. All electrons are paired (Diamagnetic).
Step 2: $S_2$ form exists in the vapor phase at high temperatures ($> 1000 \text{ K}$).
Step 3: Like $O_2$, the $S_2$ molecule has two unpaired electrons in antibonding $\pi^*$ orbitals according to Molecular Orbital Theory.
Step 4: Therefore, only $S_2$ is paramagnetic.