Elements, compounds and mixtures

Element

A pure substance that cannot be broken down into two or more simpler substances by chemical methods.

Compound

A pure substance containing two or more elements that are chemical combined in a fixed ratio.

Elements can appear as:

• atoms

• molecules

• metals (a lattice of positive ions with a ‘sea’ of delocalised electrons

Compounds formed can be:

• ionic in nature

• covalent in nature

Diff between compounds and mixtures

A compound has a fixed proportion of the different kinds of atoms it is made up of.

A mixture does not have substances in fixed ratios.

Mixtures can consist of:

different elements

different compounds

different elements and compounds

Separation of compounds of mixtures

Compounds can be broken down into their constituent elements using chemical methods (thermal decomposition, electrolysis)

Mixtures can be separated into their constituent elements and/or compounds using physical methods.