GCSE AQA Chemistry Atoms, Compounds and Mixtures

Atoms

Atom: a single particle of a particular substance/element; the smallest part of an element that can exist. 

Atoms are made of 3 subatomic particles

- Protons 

- Neutrons 

- Electrons 

Protons and neutrons have a mass of 1 and electrons have a mass of 1/1840. Protons have a +1 charge, neutrons are neutral so have a charge of 0 and electrons have a charge of -1. 

Protons and neutrons are both found in the nucleus of an atom. This is because protons, being positive, repel each other like north poles on magnets. There are neutrons in the nucleus to keep them from flying apart, acting as a 'spacer'/'glue.'

Unlike protons and neutrons, electrons are found in the energy levels (electron shells) which surrond the outside of the nucleus. 

Electron Shells:

1st shell: holds up to 2 electrons

2nd shell: holds up to 8 electrons 

3rd shell: holds up to 8 electrons

remember - shells fill from the centre outwards. 

Elements

Element: a…