4.1 Ionic bonding and structure

Define ionic bond.

Electrostatic attraction between oppositely charged ions formed by electron transfer.

What is an ion?

A charged particle formed when an atom gains or loses electrons.

Define cations.

Positively charged ions formed by loss of electrons.

Define anions.

Negatively charged ions formed by gain of electrons.

What is an ionic lattice?

A giant lattice of ions arranged in a regular, repeating pattern held by strong electrostatic forces.

Why do ionic compounds have high melting points?

Strong electrostatic attractions require large amounts of energy to break.

Why do ionic compounds conduct electricity when molten or aqueous but not when solid?

Ions are mobile in molten/solution; they are fixed in place in a solid lattice.

Define lattice enthalpy (HL).

The enthalpy change when 1 mole of an ionic solid forms from gaseous ions.

What two factors affect ionic bond strength?

Ion charge and ionic radius.

How does ionic radius affect lattice strength?

Smaller ions → stronger attraction.

How does ionic charge affect lattice strength?

Higher charges → stronger electrostatic forces.

Define polyatomic ion.

A charged species containing two or more atoms covalently bonded that act as a single ion.

State the formula and charge of the sulfate ion.

SO₄²⁻.

State the formula and charge of the nitrate ion.

NO₃⁻.

State the formula and charge of the ammonium ion.

NH₄⁺.