What everyone needs to know:
Everything is made from the approximately 100 types of atoms on the periodic table. Elements are made from one type of atom, compounds are atoms of different elements chemically combined (bonded) and mixtures are two or more elements or compounds not chemically combined.
You need to select, describe and explain techniques of separation.
You need to know about the first 20 elements only (Hydrogen to Calcium), their patterns and reactions.
The model of the atom, what it is now, how it was first described and steps along the way as the model was improved due to experimental work (links with Physics).
Particles that make up an atom, their sizes, where they are found, their charges and the structure of electron shells. You should also know the approximate sizes of atoms: radius = 0.1 nm (or 1 x 10-10 m), the radius of the nucleus is 1/10 000 of the size, (approximately 1 x 10-14 m).
Relative atomic mass, describe the symbols on the periodic table and explain the mass number and atomic number with links to isotopes.
You need to know how the periodic table was developed from the initial handful of elements known to what we have today. Describe the input that certain scientists had.
Finally, you need to know, in detail, the reactions and properties of groups 1, 7 and 0. Patterns in reactivity and size will need to be explained.
Extra topics needed for the Higher papers:
As well as word equations, you need to use and balance symbol equations.