Elements, Compounds & Mixtures (Cambridge O Level Chemistry)

Elements, compounds and mixtures

• All substances can be classified into one of these three types

Element

• A substance made of atoms that all contain the same number of protons and cannot be split into anything simpler
• There are 118 elements found in the Periodic Table

Compound

• A pure substance made up of two or more elements chemically combined
• There is an unlimited number of compounds
• Compounds cannot be separated into their elements by physical means
• E.g. copper(II) sulfate (CuSO₄), calcium carbonate (CaCO₃), carbon dioxide (CO₂)

Mixture

• A combination of two or more substances (elements and/or compounds) that are not chemically combined
• Mixtures can be separated by physical methods such as filtration or evaporation
• E.g. sand and water, oil and water, sulfur powder and iron filings 

Particle diagram showing elements, compounds and mixtures