Ernest Rutherford was a British physicist most well known for discovering the nucleus. Born on August 30, 1871 in Nelson, New Zealand, Rutherford was the fourth child in a family of twelve siblings (Nobel). Rutherford attended public schools until he was 16, at which point he received a scholarship to study at Nelson collegiate school (Nobel). In 1889, Rutherford began research at the University of New Zealand, Wellington on scholarship (Nobel). Graduating in 1893 with a double major in mathematics and physical science, Rutherford proved himself to be a talented scientist (Nobel). After graduating, he continued his work at the University of New Zealand where he earned his Bachelor's degree of science (Nobel). Following his time in New Zealand, Rutherford was awarded a scholarship to attend Trinity College, Cambridge as a research student under renowned physicist J.J. Thomson, the man who is credited with the discovery of the electron and the plum pudding model (Nobel). In 1898, he left for Canada to take up a professorship at McGill University in Montreal (Nobel). Rutherford eventually became professor of physics at the University of Manchester and then at Cambridge (Nobel).
Early Contributions to Science
Rutherford's earliest experiments had to do with the magnetization of iron. Rutherford found that alternating currents could cause a magnetized needle to lose some of its magnetization (Britannica). Rutherford also developed a more commercially effective detector of electromagnetic waves (Britannica). He was the first physicist to discover differences in types of radiation waves. Rutherford described the two types of waves as alpha and beta waves (Britannica). Rutherford later found that the alpha particles were actually the nucleus of a +2 positively charged helium-4 ion. Through his work in radiation, Rutherford developed the concept of half-life, "the interval of time required for one-half of the atomic nuclei of a radioactive sample to decay" (Britannica), which can be used an excellent elemental identifier. He developed the transformation theory, which claimed that an atom's radioactive energy came from within the atom, and the emission of an alpha or beta particle signified an elemental change (Britannica). Rutherford later proved that the alpha particles he used in his experiments were actually helium ions (Britannica). In addition, Rutherford was able to obtain a precise value for Avogadro's number (Britannica).
The Gold Foil Experiment and the Discovery of the Atomic Nucleus
Rutherford shot alpha particles into a thin strip of gold foil, and he noticed that, contrary to what he expected, some of the alpha particles deflected at angles greater than 90 degrees from their original direction. He described it as "almost as incredible as if you fired a 15-inch shell at a piece of tissue paper and it came back and hit you" (Britannica). In 1911, Rutherford determined that the atom is mostly empty space, but that there must be a dense, positively charged center of the atom that caused the alpha particles to deflect. Prior to Rutherford's discovery, the scientific community went by the plum pudding model, which said that the atom was a mix of positive space with negatively charged electrons floating in the atom. Rutherford shattered the theory by discovering the nucleus (Britannica).
After discovering the nucleus, Rutherford continued his work in radiation. He successfully provoked an artificial nuclear reaction in a stable element (Britannica). Also, he predicted the existence of a neutrally charged particle that existed in the nucleus, what is now known as the neutron (Britannica).
Presentation and Reception
Rutherford's transformation theory was controversial, but his tremendous experimental evidence supported his theory. Along with his teaching and research, Rutherford wrote the leading textbook on radioactivity titled Radioactivity in 1904 (Britannica). He received the Nobel Prize for Chemistry. In addition, Rutherford's discovery of the nucleus received little attention until the physicists Niels Bohr and Heinsenberg showed its relevance in the quantum mechanical model (Britannica). Rutherford was widely published in newspapers and magazines. His research, especially the discovery of the nucleus, was seen as hugely influential and was one of the most significant scientific developments in the 20th century.