Chemistry Revision By Saffy

Ionic bonding

Ionic bonds are very strong and require a lot of energy to break them, this means that they have a high melting point.

Properties

  • High melting point
  • Dissolves easily in water
  • Did not conduct electricity by itself
  • Does conduct electricity in water
  • Made of crystals

Covalent Bonding

Covalent bonds (only with simple molecules) have strong bonds but the molecules between them are weak, this means the have a low melting point.

Simple molecules

Simple molecules have a low melting point because it only needs a small amount of energy to separate the molecules from their solid arrangement to their liquid arrangement.

Giant covalent structures

Atoms that share electrons usually form molecules but sometimes they for giant structures

Have strong bonds that require a lot of energy to break so it has a high melting point.

Examples are graphite and diamond

Graphene and Fullerene

Simple covalent substances don't conduct electricity because there are no free ions, so there are no delocalised electrons to carry electricity.

Atoms that contain only a few atoms that are covalently bonded are called simple covalent molecules.

Fullerenes contain carbon atoms that joint to make large hollow cages which can have all sorts of shapes.

Discovered in 1985 by Sir Harry Kroto. The first fullerene discovered was buckminsterfullerene (c60).

Can be used drug delivery into the body and lubricants.

Polymers

Polymerisation is when many small molecules (monomers) join together to form a long chain.

Metallic structures

Metallic structures have crystals and giant structures so they have a high melting point.

Metals atoms donate electrons into the 'sea of electrons' that hold the metal atoms together.

With pure metals atoms slide easily over each other as they are the same size so it changes shape easily - it is softer.

In an alloy the atoms are different sizes which disrupts the pattern and makes it harder to change shape because the metals won't slide over each other.

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