p-Block Elements Summary

General Overview of p-Block Elements

  • Last electron enters outermost p orbital, leading to six groups (13-18).
  • Valence shell electronic configuration: $ns^2 np^{1-6}$ (except He).

Key Trends and Properties

  • Variation in physical properties (atomic/ionic radii, ionisation enthalpy) due to different inner cores.
  • Maximum oxidation state = total valence electrons; increases to the right in periodic table.
  • Group oxidation state most stable for lighter elements; stability of two units less increases for heavier elements (inert pair effect).

Group 13 Elements: Boron Family

  • Boron (non-metal), aluminium (metal), gallium (metal), indium (metal), thallium (metal, radioactive).
  • Boron constitutes a major part of compounds like borax (Na2B4O7·10H2O).
  • Abundant Aluminium ($8.3\%$ of earth's crust).
Important Properties
  • Atomic/ionic sizes: Ga < Al due to d-electron effects.
  • Ionization enthalpies vary, generally decreasing down the group.
  • Electronegativity decreases from B to Al, then increases slightly.

Chemical Properties

  • Boron primarily forms covalent bonds; aluminium shows +3 oxidation state.
  • Heavier Ga, In, Tl can show both +1 and +3 states, with +1 becoming more stable.
  • Reactivity towards air: Boron unreactive, Al forms protective oxide layer, reacts with O2, forming B2O3 and Al2O3.

Group 14 Elements: Carbon Family

  • Elements: Carbon, silicon, germanium, tin, lead, flerovium.
  • Carbon forms various allotropes (diamond, graphite, fullerenes) and possesses unique catenation properties.
Key Trends
  • Covalent radii increase from C to Si, minor increase to Pb.
  • Ionization enthalpy is higher than Group 13; large group stability in +4 oxidation state (C, Si predominantly).

Oxides of Carbon

  • Two important oxides: CO (neutral, strong reducing agent) and CO2 (acidic, involved in global warming).
  • Both prepared via combustion; CO2 reacts with water to form H2CO3.

Allotropes of Carbon

  1. Diamond
    • Tetrahedral sp3 hybridization, very hard, used in abrasives.
  2. Graphite
    • Layered structure with sp2 hybridization, good conductor of electricity, soft and slippery.
  3. Fullerenes
    • C60 structure; stability and unique bonding.

Important Compounds

  • Borax (Na2B4O7·10H2O): Utilized in glass manufacturing, etc.
  • Boric Acid (H3BO3): Mild antiseptic, forms tetrahedral [B(OH)4]− in water.
  • Diborane (B2H6): Toxic gas, used in many reactions.