In 1930, the physicist Paul Dirac proposed that all the fundamental particles have antiparticles whose electrical properties are opposite to the familiar particles. 

Predict the charge on the antielectron and write its nuclide symbol.

In 1932, the American physicist Carl Anderson (1905-1991) discovered the 'anti-electron' (now called a positron) by allowing cosmic rays to pass through a cloud chamber when particles and anti-particles collide they annihilate each other and are converted into energy.