Electron mass

The rest mass of the electron, m_e, is

9.109 x 10^-31 kg.

If an electron is accelerated to a significant fraction of the velocity of light (as happens for example in an electron microscope) its mass increases relativistically according to the equation:

m = m_e / Ö(1 - [v /c]²),     where

v is the velocity of the electron and

c is the velocity of light (2.998 x 10⁸ m/s)