Atoms

All atoms are made up of subatomic particles

Proton               +1                 1

Neutron               0                 1

Electron             -1               >1

In an atom, in the nucleus, there are:

• Protons and neutrons

• Nucleus is overall positive as neutrons have no charge

In the energy levels called shells, there are:

• Electrons
• Atom overall has no charge as electrons are negative in the shells

Atomic Number - Number of Protons in an element

- It is found at the bottom of an element

Mass Number - Number of Protons and Neutrons in an element

- It is found at the top of an element

• VERTICAL COLUMNS = GROUPS

• ALL ELEMENTS IN A GROUP HAVE SAME NUMBER OF ELECTRONS IN THEIR OUTER SHELL
• ELEMENTS IN GROUPS HAVE SIMILAR PROPERTIES
• HORIZONTAL = PERIODS

The pattern:

1st shell - can hold 2 electrons

2nd shell - can hold 2 electrons

3rd shell - when it holds 8 electrons

4th shell - A fourth can be made

Group 1 (The alkali metals) = 1 electron in outer shell

Group 2 (The alkaline earth metals) = 2 electrons in outer shell

Group 7 (The halogens) = 7 electrons in outer shell

Group 0 (The noble gases) = Full outer shell

• It is the process of sharing atoms

• They only share electrons in their outer shells

• Each covalent bond provides one extra shared electron for each atom

• Each atom involved has to make enough covalent bonds to fill up its outer shell

• They have no overall charge

There are very WEAK INTERMOLECULAR FORCES (BETWEEN EACH MOLECULE)

Between each ATOM, there are verySTRONG INTRAMOLECULAR FORCES

The Pattern: EXCEPT FOR B,C,Si,NE+AR

The elements Hydrogen, Lithium, Berillyum, Sodium, Magnesium, Aluminium, Potassium, Calcium LOOSE ELECTRONS TO HAVE A FULL OUTER SHELL

The elements Nitrogen, Oxygen, Fluorine, Phosphorus, Sulphur and Chlorine GAIN ELECTRONS TO HAVE A FULL OUTER SHELL