Therefore, computation of the trajectory
of an alpha-particle scattered by a single nucleus is enough Alpha-
particles are nuclei of helium atoms and, therefore, carry two units, 2e,
of positive charge and have the mass of the helium atom The charge of
the gold nucleus is Ze, where Z is the atomic number of the atom; for
gold Z = 79 Since the nucleus of gold is about 50 times heavier than an
a-particle, it is reasonable to assume that it remains stationary
throughout the scattering process