The kinetic energy of an object is the energy that it attains due to its motion. It is the work needed to accelerate a body of a given mass from rest to its stated velocity.
The formula for Kinetic energy of an electron is given as,
K.E. = e2 / 8π ε0 r
ε0 = permittivity of free space
e = Charge on an electron (1.6 x 10–19 C)
r = radius of the orbit of an electron