Refer to the periodic table and answer the following questions:
$(a)$ Select the possible non-metals that can show disproportionation reactions.
$(b)$ Select three metals that can show disproportionation reactions.

(N/A) reactant participating in a disproportionation reaction must have at least three oxidation states.
$(a)$ $P$,$Cl$,and $S$ are non-metals that exhibit more than three oxidation states,therefore they can undergo disproportionation reactions.
$(b)$ $Mn$,$Cu$,and $Ga$ are metals that can show disproportionation reactions as they also exhibit more than three oxidation states.