1.03 Atomic structure

The structure of the atom
The central part of an atom is made up of a dense nucleus. The nucleus of the atom is made up of two types of particles called protons and neutrons (some of the simpler atoms only contain protons in the nucleus). Around this nucleus orbit much less massive particles called electrons. Neutrons and protons are much more massive than electrons and therefore they make up most of the mass of the atom.

Electrical Charge
Electrons and protons possess a property called electrical charge. They each possess an equal amount of charge but they have opposite types. Protons have positive charge and electrons have negative charge. When two particles with the same type of charge are brought near to each other the particles are repelled. If the particles possess opposite charge they are attracted to each other (this is similar to the behaviour of the north and south poles of magnets.) The quantity (Q or q) of electrical charge is measured in Coulombs (C). Neutrons do not possess any electrical charge.