Electrons

ALL matter consists of atoms

Atoms contain three types of smaller particles

• Protons are positively charged;

• Electrons are negatively charged;

• Neutrons have no charge – they are neutral

  so atoms of neutrally charged with the same number of electrons and protons

Protons and neutrons are found inside the nucleus while electrons orbit the nucleus

Ions:

• 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

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

What are free electrons?

-particles in a metal are held together by strong metallic bonds

• Metals atoms have loose electrons in the outer shells, which form a 'sea' of delocalized or free negative charge around the close-packed positive ions.

These loose electrons are called free electrons.

They can move freely throughout the metallic structure

Direction of flow of free electrons

• Energy is required to make the free electrons travel in one direction.

• An electric cell (often called a battery) can supply this energy and make free electrons move in a metal conductor connected between its two terminals

Key points

• The direction of conventional current is from the positive terminal, through the conductor, to the negative terminal.

• The direction of free electron flow is from the negative terminal, through the conductor, to the positive terminal.

• The direction of conventional current is the direction marked on all circuit diagrams.

• The symbol for electric current is I.