Group 13 and 14 are p-block elements, consisting of metals, non-metals and metalloids. These elements show variable oxidation st~tes, lower oxidation state becomes more stable, when we go down the group. The combined effect of size and availability of d-orbitals influence their ability to form \(\pi\) - bonds, Lighter elements form \(p \pi-p \pi\) bonds where as heavier elements form \(d \pi-p \pi \text { or } d \pi-d \pi\) bonds.
Boron forms electron deficient compounds. AI exhibits +3 oxidation state. Tl+ is more stable than TI³⁺due to inert pair effect. Carbon is typical non-metal of group 14, shows a property of catenation and forms large number of compounds. It also shows allotropy, diamond, graphite and fullerene are crystalline allotropes of carbon. Group 14 elements show +4 and +2 oxidation states. Pb²⁺ is more stable than Pb⁴⁺.CO and CO₂ are oxides of carbon. CO2 is acidic and CO has lone pair, therefore, forms metal carbonyls. CO is deadly poisonous. CO₂ is greenhouse gas. Silica, silicates and silicones are important classes of compounds of silicon.
(a) Why is Pb⁴⁺ good oxidising agent?
(b) Why is CO deadly poisonous?
(c) Why are silicones used in implants?
(d) What is use of zeolites?
(e) Why is fullerene purest allotrope of carbons?
(f) What is structure of \(\mathrm{SiO}_{4}^{4}\) ?
(g) Why is NaOH not stored in glass bottles?

Boron is element of Group 13. It is metalloid. Borax, orthoboric acid and diborane are important compounds of boron. Borax is used to prepared heat resistant pyrex glass. It is also used for cleaning metals like gold. It is also used in borax bead test to detect coloured salts in lab.
Orthoboric acid is a weak acid used as antiseptic in eye lotion. It is solid having extensive H-bonding. It acts as Lewis acid.
Diborane is a colourless, highly toxic gas. it catches fire spontaneously upon exposure to air. It burns in oxygen releasing enormous amount of energy.
(a) Why is boric acid considered as weak Lewis acid?
(b) What happens when boric acid is heated strongly?
(c) What happens when sodium hydride reacts with B₂H₆?
(d) What happens when sodium borohydride is reacted with I₂?
(e) Give one use of NaBH₄.

Study the table of atomic and physical properties of group 14 elements and answer the questions that follow based on table and related studies concepts.
Atomic and Physical Properties of Group 14 Elements

(a) Why does carbon not form C⁴⁺ ions?
(b) Why is density of lead higher than Sn?
(c) Why is melting point of TiD lowest in group 14?
(d) Which is better conductor lead or Tin and why?
(e) Why does \(\mathrm{CF}_{6}^{2}\) Dot formed but \(\mathrm{SiF}_{6}^{2-}\)exists?
(f) Why is CO2 gas whereas Si02 solid?
(g) What is carborundum? Give its use.