Chemistry Unit 1

Atoms are the tiny particles that all substances are made from

An element is as substance which contains only one type of atom

A compound is a substance that contains two or more different types of atoms chemically joined together

A mixture is a substance which contains two or more different types of atoms or molucules not chemically joined together

The groups contain elements with similar chemical problems.

Protons, Neutrons & Electrons are not evenly distributed in an atom.

The protons and neutrons exist in a dense core at the centre of the atom. This is called the Nucleus.

The electrons are spread out around the edge of the atoms. They orbit the Nucleus in layers called Shells

Particle                      Mass                 Charge

Proton                           1                        +1

Neutron                         1                          0

Electron                         1                         -1

Electrons are not evenly spread out but exist in layers called shells.

The arrangement of the electrons in these shells is often called the Electronic Configuration.

1st shell- holds a maximum of 2 electrons

2nd shell- holds a maximum of 8 electrons

3rd shell- holds a maximum of 8 electrons

etc.

Atoms can be bonded in 2 ways;

Ionic bonding (giving electrons)                            Metal and Non-metal atoms

Covalant bonding (sharing electrons)                   Non-metal atoms only

Bonding occurs because atoms with incomplete outer electron shells are unstable. By forming bonds, atoms completely fill their outer shells and become stable.

All types of Bonding involve changes in the number of electrons in the outer shells of the atom.

Limetone is a type of sedimentry rock that is mainly composed up of calcium carbonate CaCO2

It comes from the shells of sea creatures or from solids formed in the sea long ago

It is an important raw material for both the chemical and construction industries.