State why noble gases have stable electronic configuration while atoms of other elements have unstable electronic configuration.

Define each of the following terms -

(a) electrovalent bond

(b) electrovalent compound

(c) covalent bond

(d) covalent compound

with suitable examples wherever required.

Explain in brief how atoms of other elements other than noble gases, attain stable electronic configuration of the nearest noble gas.

State what is meant by - (a) duplet rule (b) octet rule.