Electrons

Electrons are the lightest of all the sub-atomic particles

The radius of an electron is < \(10^-15\) m

Electrons are negatively charged, and have the symbol \(e^-\)

The charge of the electron was measured by Robert Millikan with his oil-drop experiment

Unlike the protons and neutrons, the electrons orbit the nucleus

In 1913, the scientist Niels Bohr proposed that the electrons were in orbits of different energy levels

The electrons enable atom to form chemical bonds

An ionic bond is when two charged atoms are attracted towards each other