Why does ice float over water?

Give reasons for the following:
(i) Density of water is maximum at 277K (4°C).
(ii) Why glycerol (glycerine) is more viscous than ethyl alcohol?

Explain the formation of a chemical bond.

Write Lewis symbols for the following atoms and ions:
S and S^2–;  Al and Al³⁺; H and H^–.

Define octet rule. Write its significance and limitations.

Write three favourable factors for formation of ionic bond.

Define bond length.

Explain the important aspects of resonance with reference to the 

Define electronegativity. How does it differ from electron gain enthalpy?

Explain with the help of suitable example polar covalent bond.