C2: Bonding and Structure

Ion

An atom or group of atoms that has an electrical charge either positive or negative

Ionic Bonding

The electrostatic force of attraction between 2 oppositely charged ions, from metal to non-metal

Ionic Compound

A giant structure of ions, called a giant ionic lattice

High melting point in Ions

The oppositely charged ions are held together by strong electrostatic forces that require a lot of energy to break.

Poor conductor of electricity when solid (ion)

Ions are in a fixed position, therefore there are no mobile charge carriers. Ions cannot move so electricity cannot flow.

Good conductor of electricity when gas/liquid (ions)

Ions are not in a fixed position, because there is enough energy to overcome the strong forces between the ions. Ions can flow and carry the current.

Soluable in water (ions)

Water molecules have a slight charge and can attract the ions away from the lattice, splitting the lattice. When dissolved, the ions are free to move and carry and electric current.

Brittle (ions)

When a lattice is hit, a layer of ions are shifted so ions with the same charge are lined up together. These charges repel and split the lattice.

Covalent Bonding

The strong electrostatic attraction between the positively charged nucleus of each atom and the negatively charged electron pair shared between them. The sharing of a pair of electrons between non-metals

Stick diagram for water

H-O-H

Low boiling point (SC)

Due to weak intermolecular forces between molecules which require little energy to overcome.

Can’t conduct electricity (Simple Covalent)

There are no charged particles to carry charge

Good insulators (Simple Covalent)

Unable to transfer thermal energy efficiently.

How many covalent bonds in a Diamond?

4 covalent bonds

Why can’t a diamond conduct electricity?

It has 4 out of 4 strong covalent bonds. There is no delocalised electron that is able to be a mobile charge carrier

How many covalent bonds in Graphite?

3 covalent bonds

Why can Graphite conduct electricity?

It has 3 out of 4 strong covalent bonds. It has a delocalised electron that can be used as a mobile charge carrier.

Why does Diamond and Graphite have high melting points?

They have strong covalent bonds that require a lot of energy to break.

What is diamond’s strength?

It’s very strong because it has 4 strong covalent bonds.

What is graphite’s strength?

Soft because of graphite’s layers and the weak intermolecular forces between them.

Metallic bonding

The strong electrostatic attraction between the positive metal ions and delocalised electrons

High melting point (M)

The strong electrostatic attraction between positive ions and delocalised electrons require a lot of energy to overcome.

Malleable and Ductile (M)

Layers of ions can slide over each other (the delocalised electrons can move, so the electrostatic attraction is maintained).

Good conductors of electricity (M)

It has a sea of delocalised electrons that are able to be mobile charge carriers.

Alloys

Mixtures of a metal with another substance.

Why can’t atoms in alloys slide over each other?

Atoms in alloys are different sizes so they form uneven layers, so they are unable to slide over each other.

How small are nanoparticles?

1-100nm

What does titanium dioxide do?

It blocks UV light and leaves no white marks on skin, whilst providing better coverage than other sunscreen.

Nanoscience

The science of structures up to a few hundred atoms wide

1m to nm

10(9)nm

1m to hm

10(6)hm

1 hm to nm

10(3)nm

Why are nanoparticles more reactive?

Nanoparticles have large exposure of atoms on their surface.

What are fullerenes?

Molecules of carbon atoms with hollow shapes.

Why do fullerenes have low melting points?

They have weak intermolecular forces which are easy to break.

Can fullerene conduct electricity?

No, because they have no delocalised electrons that can move between molecules and carry the charge.

Why are fullerenes slippery?

The shape of the molecule (ball shape) can slide over each other.

Uses of fullerene?

Can be used to carry drugs around the body

What is a nanotube?

A layer of graphene rolled into a cylinder

Can nanotubes conduct electricity?

Yes because it has delocalised electrons that can move along the tube and carry current.