RBSE Class 12 Chemistry Notes Chapter 7 The p-Block Elements

These comprehensive RBSE Class 12 Chemistry Notes Chapter 7 The p-Block Elements will give a brief overview of all the concepts.

RBSE Class 12 Chemistry Chapter 7 Notes The p-Block Elements

→ General electronic configuration of the elements of group-15 is ns² np³.They are collectively known as pnicogen (suff ocation creating).

→ N₂O is known as 'laughing gas'.

→ Ammonia can be prepared on large scale by Haber's process.

→ Nitrogen gas is inert under ordinary conditions because it has very high dissociation energy (945 kj mol^-1) due to the presence of triple bond.

→ Phosphorus exist in various allotropic forms i.e. white, red and black phosphorus, the yellow or white allotropic form of phosphorus is very reactive and poisonous in nature. It readily catches fire when exposed in air. It causes phossy jaw disease. White phosphorus is stored under water.

→ Some properties of hydrides of group-15 are as follows: ,
(a) NH₃ > PH₃ > ASH₃ > SbH₃ > BiH₃ (Basic character)
(b) NH₃ > PH₃ > ASH₃ > SbH₃ > BiH₃ (Bond angle)
(c) NH₃ > PH₃ > ASH₃ > SbH₃ > BiH₃ (Thermal Stability)
(e) NH₃ < PH₃ < ASH₃ < SbH₃ < BiH₃ (Reducing Nature)

→ The hydride of phosphorus is known as phosphine (PH₃) which is highly poisonous in nature.

→ Nitric acid (HNO₃) was earlier called as aqua fortis (meaning strong water).

→ Pure PH₃ does not spontaneously inflame. It bums in air or oxygen at 423 K. The spontaneous inflammability at the time of preparation (due to the presence of P₂H₄) is used in making Holme's signals.

→ Group-16 has fine elements i.e. O, S, Se, Te and Po. The general electronic configuration of these elements is ns2 np4. It show maximum oxidation state + 6. They are collectively called as chalcogens (ore forming).

→ Some important properties of these hydrides are as follows:
(a) H₂O > H₂S > H₂Se > HeTe (Thermal stability)
(b) H₂O < H₂S < H₂Se < H₂Te (Reducing character)
(c) H₂S < H₂Se < H₂Te < H₂O (Volatility) ,
(d) H₂O < H₂S < H₂Se < H₂Te (Acidic behaviour)
(e) H₂O > H₂S > H₂Se > H₂Te (Bond angle)
(f) H₂O < H₂S < H₂Se < H₂Te (Covalent character)
(g) H₂O < H₂S < H₂Se < HeTe (m.pt and b.pt.)

→ Sulphur forms various oxyacids like H₂SO₄ (Sulphuric acid), H₂SO₃ (Sulphurous acid), H₂S₂O₇ (Peroxodisulphuric acid), H₂S₂O₇ (Pyrosulphuric acid). Among these oxoacids H₂SO₄ is very important. It is a strong dibasic acid. It is known as oil of vitriol. It can be prepared by contact process.

→ The oxides are classified as:
(a) Acidic Oxides: CO₂, SO₂, Cl₂O₇, P₂O₅, SiO₂ etc. (Oxides of non-metals)
(b) Basic Oxides: Na₂O, MgO, CuO, PbO, CaO etc. (Oxides of metals)
(c) Neutral Oxides: CO, N₂O, NO, H₂O etc.
(d) Amphoteric Oxides: ZnO, Al₂O₃, PbO₃, PbO₂, SnO₂ etc.
(e) Mixed Oxides or Sequioxides: Fe₃O₄, Pb₃O₄, Mn₃O₄ etc.

→ The name sulphur has been derived from sulveri meaning killer of copper. Sulphur dioxide (SO₂) behave as bleaching agent. The bleaching action of SO₂ is unstable because it is due to reduction process while the bleaching action of Cl₂ is permanent because it is due to oxidation process.