FUNDAMENTAL IDEAS

All substances are made of elements, these are listed in the periodic table. 

Each element is made from one type of atom. These atoms are represented by chemical symbols (e.g. Carbon = C)

The periodic table is arranged into groups, groups tell us how many electrons are on the outer shells of those elements (e.g. elements in group 2 have 2 electrons on their outer shells). Elements also usually have similar properties due to this.

Each atom has a nucleus made up of protons and nuetrons, this is surrounded by elelctrons.

When elements react with eachother a compound is formed. This is a mixture of elements chemically bonded together.

Group 1 metals are alkali metals.

Group 2 metals are alkaline earth metals.

Transiton metals are inbetween groups 2&3.

Group 7 are the halogens.

Group 8/0 are the noble gases.

In the nucleus there are:

Protons with a posotive charge

Nuetrons with no charge.

Electrons which travel around the nucleus have a negative charge. Atoms have no overall charge due to the number of protons and electrons cancel eachother out.

Atomic numbers represent the number of protons and electrons in an atom.

The mass number is the total number of protons and neutrons.

Shells represent atoms energy levels, electrons with the lowest energy level are closest to the nucleus.

The first shell holds 2 electrons, further shells can hold up to 8 electrons.

Elements in the same group of the periodic table have the same amount of electrons on the outer shells or highest energy level (e.g. Group 1 elements have 1 electron on their outer shell).

Group 1 elements include of Lithium, Sodium & Potassium, these all react quickly with water and oxygen. This is because they're unstable as they only have one electron on their outer shell and want to lose it.

Contrastingly, the noble gases group 8/0 are extremely unreactive as they have full outer shells and are not looking to lose or gain any electrons.

Different elements combining forms compounds. When a metal reacts with with a non-metal it forms an ionic bond. Ions have a charge. 

The chemical formula tells us the ratio of ions in the compound. NaCl shows there are equal numbers of Sodium and Chlorine in the ion.

Non-metals bonding with non-metals form covalent bonds. Electrons are shared between atoms. Covalent bonds can be drawn as lines between atoms that are bonded together.

In chemical reactions, reactants react together to form products. This reaction can be shown through chemical equations. Word equations give the names of the reactants and products, but symbol equations can show the number of atoms in the reactnnts and products. This helps to check if they're balanced.