Bonding

Define IONIC, COVALENT & METALLIC BONDING:

• Ionic: the electrostatic force of attraction beween oppositely charged ions in a lattice.

• Covalent: the strong electrostatic force of attraction a shared pair of electrons.

• Metallic: the attraction between delocalised electrons and positive ions arranged in a lattice.

What is the structure and properties [3] of IONIC LATTICES?

→ Structure:

Ions are held by strong ionic bonds in a lattice.

→ Properties:

Has high melting & boiling points. Conducts electricity when molten or dissolves in solvent. Is brittle.

What is the structure [2] and properties [4] of METALLIC LATTICES?

→ Structure:

Positive ions surrounded by a sea of delocalised electrons. In a regular arrangement.

→ Properties:

High melting & boiling points. Conducts electricity. Conducts heat. Is malleable.

What is the structure and properties [2] of SIMPLE COVALENT LATTICES?

→ Structure:

Ions held by weak intermolecular forces in a lattice.

→ Properties:

Low melting & boiling points. Can't conduct electricity.

What is the structure and properties [2] of GIANT COVALENT LATTICES?

→ Structure:

Ions held by strong covalent bonds in a lattice.

→ Properties:

High melting & boiling points. Can't conduct electricity (except graphite).

What is ELECTRONEGATIVITY [3]? What is the trend of electronegativity down a group & across a period?

The power an atom has at attracting the pair of electrons in a covalent bond. This makes 1 atom delta- and the other atom delta+. If atoms have the same electronegativity the bond is non-polar.

• Across a PERIOD electronegativity increases, due to the number of protons increasing.

• Down a GROUP electronegativity decreases, due to the increase in shielding.

Why so some polar molecules no have a permanent DIPOLE [2]?

• Polar molecules is when their individual dipoles don't cancel out (Asymmetrical shape).

• Some don't have permanent dipoles due to their dipoles cancelling themselves out. / They have symmetrical dipoles.

What are the different types of INTERMOLECULAR FORCES [3]? (in order of strongest to weakest)

• Hydrogen bonds: between a hydrogen & lone pair.

• Permanant dipole-dipole: between 2 molecules with permanent dipoles.

• Van der Waals/Induced dipole-dipole: when electron fluctuations occur inducing a dipole, this then induces a dipole in another molecule. However this randomally breaks and reforms.

Why does water expand when frozen [4]?

• Water is held together by hydrogen bonds.

• In liquids molecules are free to move.

• While in solids they aren't free to move, so their bonds are frozen in place at certain distances.

• This makes ice less dense than water, the ice insulates the water below to reduce heat loss.