Protons, Neutrons & Electrons
- Atoms are the building blocks of all matter
- They are incredibly small - for instance, about one hundred million atoms could fit side by side across your thumbnail
- Atoms have a tiny, dense nucleus at their centre, with electrons orbiting around the nucleus
- The nucleus is made up of protons and neutrons
- The radius of the nucleus is over 10,000 times smaller than the whole atom, but it contains almost all of the mass of the atom
Diagram showing the structure of a Lithium atom. If drawn to scale then the electrons would be around 100 metres away from the nucleus!
Parts of the Atom
- The nucleus contains:
- Protons - positively charged particles with a relative atomic mass of one unit
- Neutrons – no charge, and also with a relative atomic mass of one unit
- Almost all of the atom is empty space, but moving around the nucleus there are:
- Electrons – negative charge with almost no mass (1/2000 the mass of a proton or neutron)
- The properties of each of the particles are shown in the table below:
Examiner Tip
There are many different models of the atom, such as the Plum Pudding Model. But for your exam, make sure to only use the model and descriptions described here!
