Assign reason for the following:
(a) Noble gases are mostly inert
(b) Bismuth is a strong oxidising agent in pentavalent state.

Explanation

(a) It is due to stable electronic configuration and high ionisation potential of noble gases.
(b) Bi(+3) is more stable than Bi(+5) due to inert pair effect. That is why Bi(+5) gains two electrons to form Bi(+3) and acts as an oxidising agent
`Bi^(5+) + 2e^(-) to Bi^(3+)`