Chemical bonding, hybridization, crystal lattices

Types of bonds

• Nonpolar covalent: identical atoms (H₂, O₂, Cl₂).
• Polar covalent: HCl, H₂O, NH₃.
• Ionic: metal + nonmetal (NaCl). The difference in electronegativity is large.
• Metallic bonding.
• Donor-acceptor mechanism: NH₄⁺ and H₃O⁺ are formed.
• NH₄Cl contains ionic, polar covalent and donor-acceptor bonds.

Bonds and hybridization

• A single bond is σ.
• Double bond: 1σ + 1π.
• Triple bond: 1σ + 2π.

Hybrid	Example	Angle	Shape
sp³	CH₄: sp³ hybridized	109°28′	tetrahedral
sp²	C₂H₄	120°	planar
sp	C₂H₂: sp hybridized	180°	linear

H₂O: sp³, bond angle 104.5°. NH₃: sp³, 107°.

Crystal lattices

Types: atomic, molecular, ionic and metallic.

• Atomic lattice: diamond, SiO₂. Very hard, high melting point.
• Molecular lattice: ice, I₂, CO₂. Melts at low temperatures.
• Ionic (NaCl): brittle, the melt and the solution conduct electric current.
• Metallic: conducts electricity and heat.

Also worth knowing

• Hydrogen bonding: H₂O, NH₃, HF, alcohols.
• Most electronegative: fluorine (F).