Chemistry of p-Block Elements - Detailed Notes for JEE Aspirants

Group 13 Elements

General Characteristics

• Elements in Group 13 belong to the boron family.
• Electronic configuration: ns2np1
• Common oxidation states: +3
• All group 13 elements are solids at room temperature.
• They have high melting and boiling points due to strong covalent bonds.
• Group 13 elements are relatively rare in the Earth’s crust.

Occurrence and Properties

• Boron: Occurs as boric acid (H3BO3) and borax (Na2B4O7·10H2O).
• Aluminum: Most abundant metal in the Earth’s crust, occurs as bauxite (Al2O3·xH2O).
• Gallium: Rare metal, obtained as a byproduct of aluminum production.
• Indium: Rare metal, used in making semiconductors and alloys.
• Thallium: Toxic heavy metal, used in electronics and medicine.

Preparation and Properties of Boron Compounds

Borax (Na2B4O7·10H2O):

• Prepared by reacting boric acid with sodium carbonate.
• White crystalline solid, soluble in water.
• Used as a flux in soldering and brazing, as a water softener, and as a cleaning agent.

Boric Acid (H3BO3):

• Weak acid, occurs naturally in volcanic regions.
• White crystalline solid, soluble in water.
• Used as an antiseptic, eyewash, and flame retardant.

Borohydrides:

• Compounds containing the BH4- ion.
• Sodium borohydride (NaBH4) and lithium borohydride (LiBH4) are common borohydrides.
• Reducing agents, used in organic synthesis.

Structural Aspects of Boranes

• Boranes are molecules that contain boron and hydrogen atoms.
• They have a variety of structures, including:
  • Monomers: BH3, BH2CH3
  • Dimers: B2H6
  • Polymers: B4H10, B5H9, etc.
• The structures of boranes can be explained using the valence electron counting method (VECM).

Group 14 Elements

General Characteristics

• Elements in Group 14 belong to the carbon family.
• Electronic configuration: ns2np2
• Common oxidation states: +4, -4 (for carbon only)
• Group 14 elements can be classified into three categories:
  • Typical metals: Ge, Sn, Pb
  • Metalloids: Si, Ge
  • Nonmetals: C

Occurrence and Properties

• Carbon: Occurs as graphite, diamond, and fullerene.
• Silicon: Second most abundant element in the Earth’s crust, occurs as silica (SiO2).
• Germanium: Rare metal, used in semiconductors and transistors.
• Tin: Soft, malleable metal, used in making cans, solders, and alloys.
• Lead: Toxic heavy metal, used in batteries, ammunition, and pigments.

Carbon Family

• Allotropes of Carbon:

  • Graphite: Soft, black solid with a layered structure. Good conductor of electricity.
  • Diamond: Hard, transparent solid with a cubic structure. Poor conductor of electricity.
  • Fullerenes: Carbon molecules with hollow, cage-like structures. Examples include C60 (buckminsterfullerene) and C70.

• Properties and Applications of Carbon Monoxide, Carbon Dioxide, and Carbon Disulfide:

  • Carbon Monoxide (CO): Colorless, odorless, poisonous gas. Produced by incomplete combustion of carbon-containing fuels.
  • Carbon Dioxide (CO2): Colorless, odorless, non-flammable gas. Produced by the respiration of animals and plants and by the burning of fossil fuels.
  • Carbon Disulfide (CS2): Colorless, flammable liquid with a pungent odor. Used as a solvent and in the production of rayon and cellophane.

Group 15 Elements

General Characteristics

• Elements in Group 15 belong to the nitrogen family.
• Electronic configuration: ns2np3
• Common oxidation states: -3, +3, +5
• Group 15 elements can be classified into two categories:
  • Typical nonmetals: N, P, As, Sb
  • Metals: Bi

Occurrence and Properties

• Nitrogen: Most abundant element in the atmosphere, occurs as N2 gas.
• Phosphorus: Occurs as phosphate minerals, such as apatite (Ca5(PO4)3F).
• Arsenic: Toxic metalloid, occurs as arsenopyrite (FeAsS).
• Antimony: Brittle, silvery-white metal, used in alloys and semiconductors.
• Bismuth: Heavy, brittle metal, used in alloys, pharmaceuticals, and cosmetics.

Preparation and Reactions of Nitrogen Compounds

• Ammonia (NH3):

  • Prepared by the Haber process (reaction of N2 and H2 gases at high temperature and pressure).
  • Colorless, pungent gas, soluble in water.
  • Used in the production of fertilizers, nitric acid, and explosives.

• Nitric Acid (HNO3):

  • Prepared by the Ostwald process (oxidation of ammonia).
  • Colorless, corrosive liquid, soluble in water