Bonding and shapes of molcules

Properties of metallic structures

• High melting point

• Not soluble in water

• Conducts electricity

What structure do ionic substances form

Giant ionic lattices. The ions arrange themselves to maximise attraction and minimise repulsion

Properties of ionic substances

• High melting point

• Soluble in water

• Conduct electricity when molten or dissolved in aqueous solution

Properties of covalent network

• High melting point

• Not soluble in water

• Does not conduct electricity (except graphite)

Properties of simple molecular substances

• Low melting point

• Not soluble in water

• Does not conduct electricity

Ionic bonding

The electrostatic force of attraction between oppositely charged ions

Covalent bonding

Shared electrons between 2 atoms in which the nuclei of the atoms are electrostatically attracted to the shared electrons

Dative (coordinate) covalent bonding

Both electrons in a covalent bond are supplied by 1 atom

What are some exceptions to the octet rule

BF₃ (Boron has 6 e^-) and SF₆ (Sulfur has 12 e^-)

Metallic bonding

Electrons in the outer shell of the metal atoms are delocalised leaving positive metal ions. The metal cations are electrostatically attracted to the electrons

Electron pair repulsion theory

Electron pairs repel each other as far apart as possible

Shape and bonding angle of molecules with 2 bonding pairs around central atom

Linear, 180^o

Shape and bonding angle of molecules with 3 bonding pairs around central atom

Trigonal planar, 120^o

Shape and bonding angle in SO₂

Bent, 120^o: Double bonds cancel out the extra repulsion from lone pair

Shape and bonding angle of molecules with 4 bonding pairs around central atom

Tetrahedral, 109.5^o

Shape and bonding angle of molecules with 3 bonding pairs and 1 lone pair around central atom

Trigonal pyramidal, 107^o

Shape and bonding angle of molecules with 2 bonding pairs and 2 lone pairs around central atom

Bent, 104.5^o

Shape and bond angle of molecules with 5 bonding pairs around central atom

Trigonal bipyramidal, 120^o and 90^o

Shape and bonding angle of molecules with 6 bonding pairs around central atom

Octahedral, 90^o