Ernest Rutherford was a British physicist who made many significant contributions to the fields of radioactivity and nuclear physics. Some of his key discoveries and accomplishments include:

• Radioactivity: Rutherford was the central figure in the study of radioactivity and discovered that there were at least two distinct types of radiation: alpha radiation and beta radiation. He also advanced the hypothesis that helium gas could be formed from radioactive substances.

• Nuclear atom: Rutherford postulated the nuclear structure of the atom, which showed that the atom is mostly empty space surrounding a massive nucleus. He discovered alpha and beta rays, set forth the laws of radioactive decay, and identified alpha particles as helium nuclei.

• Atomic nucleus: In 1911, Rutherford discovered the atomic nucleus using a "scattering" experiment, where he sent alpha particles through a thin sheet of gold foil and observed how the particles scattered off the gold atoms. Most passed through the foil, but a few particles bounced back, which led him to conclude that there was a dense, positively charged central region containing most of the atomic mass.

• Nobel Prize: Rutherford received the Nobel Prize in Chemistry in 1908 "for his investigations into the disintegration of the elements, and the chemistry of radioactive substances".

Rutherford was a consummate experimentalist who made many new discoveries in both radioactivity and nuclear physics. He was also a talented mentor who worked creatively with associates, some of whom were already established at the institutions to which he was appointed and others of whom he attracted as doctoral or postgraduate students.