Tamilnadu Samacheer Kalvi 12th Chemistry Notes Chapter 2 p-Block Elements-I Notes

p-Block elements have a general electronic configuration of ns2, np1-6

Catenation:
Carbon(atom) has a greater tendency to join a chain of bonds with itself or with other atoms which is known as catenation.

Inert pair effect:
The outer s electrons(ns) have a tendency to remain inert and show reluctance to take part in the bonding, which is known as inert pair effect.

Allotropism:
Some elements exist in more than one crystalline or molecular forms in the same physical state. This phenomenon is called allotropism.

Uses of boron:

  • Boron isotope – 10B5 is used as moderator in nuclear reactions.
  • Amorphous boron is used as a rocked fuel igniter.
  • Boron is essential for the cell walls of plants.

Uses of boric acid:

  • To manufacture of pottery glazes, glass, enamels and pigments.
  • It is used as an antiseptic and as an eye lotion.
  • It is also as a food preservative.

Uses of borax:

  • Borax is used for the identification of coloured metal ions.
  • In the manufacture optical and borosilicate glass, enamels and glazes for pottery.
  • It is also used as a good preservative.

Hydroboration: Diborane adds on to alkenes and alkynes in ether solvent at room temperature. This reaction is called hydroboration.

Uses of diborane:

  • It is used as a high energy fuel for propellant.
  • It is used as a reducing agent in organic chemistry.
  • It is used in welding torches.

Uses of boron trifluoride:

  • BF3 is used for preparing HBF4, a catalyst in organic chemistry.
  • It is also used a fluorinating reagent.

McAfee process:
Aluminium chloride is obtained by heating a mixture of alumina and coke in a current of chlorine.

Uses of aluminium chloride:

  • Anhydrous AlCl3 is used as a catalyst in friedel crafts reactions.
  • It is used for the manufacture of petrol by cracking the mineral oils.
  • It is used as a catalyst in the manufacture on dyes, drugs and perfumes.

Uses of Alum:

  • It is used for purification of water.
  • It is used for water proofing and textiles.
  • It is employed as a styptic agent to arrest bleeding.

Fischer Tropsch synthesis:
The reaction of carbon monoxide with hydrogen at a pressure of less than 50 atm using metal catalysts at 500 – 700 K yields saturated and unsaturated hydrocarbons.

Uses of carbon monoxide:

  • Equimolar mixture of hydrogen and carbon monoxide – water gas and the mixture of carbon monoxide and nitrogen – producer gas are important industrial fuels
  • Carbon monoxide is a good reducing agent and can reduce many metal oxides to metals.
  • Carbon monoxide is an important ligand and forms carbonyl compound with transition metals

Water gas equilibrium:
The equilibrium involved in the reaction between carbon dioxide and hydrogen, has many industrial application and is called water gas equilibrium.

Uses of carbon dioxide:

  • Carbon dioxide is used to produce an inert atmosphere for chemical processing.
  • Biologically, it is important for photosynthesis.
  • It is also used as fire extinguisher and as a propellent gas.
  • It is used in the production of carbonated beverages and in the production of foam.

Uses of Silicon tetrachloride:

  • Silicon tetrachloride is used in the production of semiconducting silicon.
  • It is used as a starting material in the synthesis of silica gel, silicic esters, a binder for ceramic materials.

Uses of Silicones:

  • Silicones are used for low temperature lubrication and in vacuum pumps, high temperature oil baths etc…
  • They are used for making water proofing clothes
  • They are used as insulting material in electrical motor and other appliances
  • They are mixed with paints and enamels to make them resistant towards high temperature, sunlight, dampness and chemicals.

Silicates:
The mineral which contains silicon and oxygen in tetrahedral [SiOJ4~ units linked . together in different patterns are called silicates.

Types of Silicates:
(i) Ortho silicates (ii) Pyro silicates (iii) Cyclic silicates (iv) Ino silicates (v) Phyllo silicates (vi) Tecto silicates.

Zeolites: Zeolites are three dimensional crystalline solids containing Al, Si and Oxygen in their regular three dimensional frame work. They are hydrated sodium alumino silicates.

Some of common allotropes of p-block elements

Element Most common allotropes
Boron Amorphous boron, α-rhombohedral boron, β-rhombohedral boron, γ-orthorhombic boron, α-tetragonal boron, β-tetragonal boron
Carbon Diamond, Graphite, Graphene, Fullerenes, Carbon nanotubes
Silicon Amourphous silicon, crystalline silicon
Germanium α-germanium, β-germanium
Tin Grey tin, white tin, rhombic tin, sigma tin
Phosphorous White phosphorous, Red phosphorous, Scarlet phosphorous, Violet phosphorous, Black phosphorous.
Arsenic Yellow arsenic, gray arsenic & Black arsenic
Antimony Blue-white antimony, Yellow, Black
Oxygen Dioxygen, ozone
Sulphur Rhombus sulphur, monoclinic sulphur
Selenium Red selenium, Gray selenium, Black selenium, Monoclinic selenium,
Tellurium Amourphous & Crystalline

Samacheer Kalvi 12th Chemistry Notes

Leave a Reply

Your email address will not be published. Required fields are marked *