Each element has a different symbol Chemical Formula Each element has a different symbol The formula for a compound shows the elements in the compound It also shows the ratio of the atoms of different elements in the compound Chemical Formula

The Periodic Table The Periodic Table

Chemical Formula Chemical Formula

Atomic Structure Atomic Structure

Electron shells Electron shells

Electron shells Electron shells

Word equations Word equations use the names of the reactants and products to describe a reaction Word equations

Word equations Word equations

Therefore chemical equations must be balanced Chemical equations use the chemical formulae of the reactants and products to describe a reaction The total mass of the product(s) of a chemical reaction must equal the total mass of the reactant(s) Therefore chemical equations must be balanced The total number of atoms of one element should be the same on both sides of the equation Chemical equations

Balancing equations Balancing equations

Relative atomic masses Atoms of different elements have different masses The relative atomic mass (Ar) is the mass of the elements compared to the mass of a hydrogen atom Relative atomic masses

Relative atomic masses

Relative Formula Mass The relative formula mass (Mr) is the relative mass of a molecule compared to the mass of a hydrogen atom Relative formula mass

Relative formula mass Relative formula mass

Equation calculations The unknown mass of a reactant or product can be worked out by using the known masses of the other reactants and products Equation calculations

Calculations from equations

Calculations from equations