As the gold foil is very thin, it
can be assumed that a-particles will suffer not more than one scattering
during their passage through it 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