The electron as a bullet

It has a mass of 9*10^-31 kg or 1 two thousandth of the mass of a proton (or one million millionth of the mass of a speck of dust).

Electron tracks
(Source: CERN (www.cern.ch/))

When the electron is shot out of the muzzle of an electron gun it emerges with a particular velocity and travels along a well defined trajectory. The electron carries a precise charge of 1.6*10^-19 coulombs. By careful design, an electron gun can make the electrons spin - like the rifling inside the barrel of a gun can make bullets spin.

All attempts to measure the radius of the electron have failed! All we know is that the radius is less than 10^-18 m; that is, its radius is one hundred million times smaller than that of the atom. All the known properties of the electron are consistent with the assumption that its radius is zero. As far as we know, the electron has no structure.

What is puzzling is how a particle can have no size and no structure and yet can have a definite mass and behave as though it is spinning? We do not know the answers to these questions but scientists are working on experiments to find out.

The electron as a wave

Confine an electron, or constrict its freedom of movement and the bullet looks like a wave. Think of an atom - say, hydrogen. The electron orbits the nucleus; in the case of hydrogen the nucleus is a single proton. Instead of a neat circular orbit the electron flies around the proton appearing at all points almost simultaneously. It behaves like a wave.

If we bring two atoms close together, their electron clouds may merge. If the electron clouds merge we get a molecule. In metals the electron waves spread out over the whole volume of the material.

Antimatter

What about the positron? The free positron is also a bullet; it has the same mass as the electron and carries an equal and opposite amount of charge. Bring a positron and an electron together and they will annihilate to give ENERGY!