(a) Complete the following chemical equations :
(b) Explain the following observations :
(i) Phosphorus has greater tendency for catenation than nitrogen.
(ii) Oxygen is a gas but sulphur a solid.
(iii) The halogens are coloured. Why?
(b) (i) The self linking property or catenation property of nitrogen is less than that of phosphorus because N-N bond is weaker than P-P bond.
(ii) Oxygen forms a stable diatomic molecule. In molecule two atoms of oxygen have joined together through double bond OO. The multiple bonding is possible due to small size of oxygen atoms. So oxygen is a gas. S has eight atoms arranged in the form of a puckered ring per molecule in which two sulphur atoms are joined by covalent bonds. So sulphur is a solid at room temperature.
(iii) All halogens are coloured. This is due to absorption of radiation in visible region which results in the excitation of outer electrons to higher energy level. So they display different colours.