ABSTRACT
In 1913, Rutherford performed an experiment in which a small positively charged alpha particle (discussed below) was scattered from a piece of gold. e large repulsive force that was observed indicated that the alpha particle had come very close to an intense positive charge. In this way it was deduced that an atom consists of a very small positively charged nucleus surrounded by electrons. e radius of the nucleus was ten thousand to one hundred thousand times smaller than that of the atom. It was determined that dierent chemical elements had dierent numbers of electrons in the atom. is is called the atomic number, Z. e charge of all electrons is –Ze, and the charge of the nucleus is +Ze, making the atom
electrically neutral.* e value of Z varies from 1 to 92, as we go from hydrogen to uranium in the periodic table.
