GCSE AQA Chemistry - Bonding, Structure and Properties of Matter

Ions

Charged particles (single atoms or groups of atoms)

Ionic bonding

In the reaction, the metal loses electrons to form a positive ion, and the non-metal gains electrons to form a negative ion. Their oppositely charged ions are attracted by electrostatic force.

Giant ionic lattice

The structure of an ionic compound, in which ions are closely packed together in a regular lattice arrangement with strong electrostatic forces between ions in all directions.

Similar properties of ionic compounds

• High melting/boiling point - strong electrostatic forces

• Conduct electricity when molten/aqueous

6 Simple molecular substances

• Hydrogen H₂

• Chlorine Cl₂

• Nitrogen N₂

• Methane CH₄

• Water H₂O

• Hydrogen Chloride HCl

Simple molecular substances

Made up of molecules containing a few atoms joined together by covalent bonds.

Properties of simple molecular substances

• Low melting/boiling points - weak IM forces

• Don’t conduct electricity

Polymers

Long molecules of small repeating units linked together.

Format of molecular formula of a polymer

• Molecular formula of repeating unit in brackets

• n outside

Giant covalent structures

All atoms are bonded to each other by strong covalent bonds.

Diamond

Each carbon atom has 4 strong covalent bonds.

Diamond and silicon dioxide properties (3)

• High melting point

• Hard

• Does not conduct electricity

Silicon dioxide

Each silicon atom forms 4 strong covalent bonds to 4 oxygen atoms.

Graphene

A single layer of graphite.

Graphite

Each carbon atom forms 3 strong covalent bonds with three other carbon atoms, and layers in the structure are bonded by weak intermolecular forces.

Properties of graphene

• High melting point

• Hard/soft

• Good conductor of electricity

Properties of graphite

• High melting point

• Soft - layers can slide over each other

• Good conductor of electricity - delocalised electrons can move through the structure

Fullerenes

Molecules of carbon atoms shaped like closed tubes or hollow balls.

Buckminster fullerene

The first discovered fullerene (C₆₀)

Three uses of fullerenes

• To deliver drugs by trapping molecules inside the structure

• As catalysts because of their large surface area

• As lubricants

Nanotubes

Cylindrical fullerenes with a high length to diameter ratio.

properties of nanotubes

• High tensile strength

• Good thermal/electrical conductors

Two uses of nanotubes

• Nanotechnology (technology that uses very small particles)

• In electronics

• To strengthen materials without adding much weight

Describe metallic bonding

Strong electrostatic forces of attraction between metal atoms and delocalised electrons hold the atoms together in a strong, regular structure.

Why are most metals solid at room temperature?

Because of strong electrostatic forces, which need large amounts of energy to overcome, giving them a high melting point.

Malleable

Can be bent or hammered into a different shape.

Why are alloys harder than pure metals?

Because there are different sized atoms, the layers will be more distorted and therefore harder to slide over each other.

Coarse particles diameter

between 2.5×10^-6m and 1×10^-5m

Fine particles diameter

between 2.5×10^-6m and 1×10^-7m

Nanoparticles diameter

between 1×10^-7 and 1×10^-9

Why are nanoparticles useful as catalysts?

Because of the greater surface area to volume ratio of nanoparticles, less of the material is needed to work as an effective catalyst.

Uses of nanoparticles

medicine, cosmetics, technology and as catalysts

What is the issue with use of nanoparticles?

• The effects on human health may not have been properly investigated

• Long-term impacts on health are unknown