Give reasons for the following: (i) Oxygen is a gas but sulphur is a solid. (ii) O3 acts as a powerful oxidizing agent. (iii) BiH3 is the strongest reducing agent amongst all the hydrides of group 15 elements.

i. In oxygen molecule, intermolecular forces are weak van der Waal's forces which causes it to exist as a gas while in sulphur, strong S=S is not formed so it exists in a puckered structure and is held together by covalent bonds and exists as a polymeric molecule.
ii. Ozone acts as a powerful oxidizing agent as it can produce nascent oxygen.
iii. On moving from top to bottom in hydrides of group 15, bond length increases and the chances of hydrogen removal also increases so oxidation number also increases and BiH3 is the strongest reducing agent amongst all the hydrides of group 15.