Electrical charges

All matter consists of atoms.

Atoms contain three types of smaller particles: protons, neutrons and electrons.

  • Protons are positively charged;
  • Electrons are negatively charged;
  • Neutrons have no charge – they are neutral.

Protons and neutrons are found inside the nucleus.

Electrons orbit the nucleus.

Image of bohr atom model with two energy levels, black dot in centre is the nucleus, two electrons in the first energy level and one electron in the second energy level.Electrons orbit a nucleus

An atom has a neutral charge, because it contains the same number of protons and electrons.

If it loses an electron, it becomes a positively charged ion.

If it gains an electron, it becomes negatively charged ion.

Charged atoms are called ions.

An electric current is a flow of charged particles in one direction.

In solids, an electric current is the flow of free electrons in one direction.

Key points

  • An electric current is a flow of charged particles in one direction.
  • Metals are good conductors of electricity because they contain free electrons.
  • Insulators such as plastic and rubber do not generally contain free electrons and so are poor conductors of electricity.
Good conductors of electricityInsulators or poor conductors of electricity
SilverRubber
CopperPlastic
AluminiumGlass
SteelWood
GoldMarble