New Zealand physicist Ernest Rutherford was already famous for his work with atoms. He knew that an atom has a nucleus (center) with a positive charge and that the nucleus is surrounded by tiny negative particles called electrons.
In 1916, Rutherford was experimenting with radioactive material. A year later he discovered he could break up the nuclei of nitrogen atoms by firing radioactive particles at them. The nuclei fragments moved incredibly fast and released a huge amount of energy. This is called a nuclear reaction.
Rutherford became the first person to split an atom — that’s how most people describe his achievement, but more accurately, what he did was split the nucleus of an atom. As well, when he split the atom, he discovered and named the proton, a positively charged particle in the nucleus of the atom.
People now call Rutherford the father of nuclear physics. His work opened doors to new ideas in physics and to the development of the nuclear power industry.
What Rutherford could not have foreseen was that splitting the atom would also lead to the creation of the nuclear, or atomic, bomb (page 91), which destroyed the Japanese cities of Hiroshima and Nagasaki in 1945.