(a) Why are ionic compounds usually hard crystalline solids ? (b) Give two methods to prevent rusting of iron. (c ) Name the ores of the metals (i) mercury (ii) zinc.

(a) Why are ionic compounds usually hard crystalline solids ? (b) Giv

1.	(a) Why are ionic compounds usually hard crystalline solids ? (b) Give two methods to prevent rusting of iron. (c ) Name the ores of the metals (i) mercury (ii) zinc.
Answer» Solution :(a) In ionic compounds, the cations and anions are closely packed in space and have strong forces of interaction. They exist as crystals which are quite HARD. (b) (i) Coating the surface of iron with zinc (galvanisation) (ii) Painting the surface of iron with a rust PROOF paint. (c ) Mercury : CINNABAR or mercury (II) sulphide (HGS) Zinc : Zinc blende or zinc (II) sulphide (ZnS)