Ernest Rutherford & Niels Bohr

1. Ernest Rutherford & Niels Bohr Atomic Theorists

2. Ernest Rutherford • Born in New Zealand on August 30, 1871 • Had six brothers and five sisters • Received degrees in mathematics and physical science from Canterbury College and graduated in 1893 • Researched under J.J. Thompson • In 1911, made his greatest contribution to physics- discovering the nucleus • Also studied radioactivity • Married and had one daughter • Died on October 19, 1937

3. Niels Bohr • Born on October 7, 1885 in Copenhagen, Denmark • Received his doctorate in physics from Copenhagen University in 1911 • Studied under J.J. Thomas and Ernest Rutherford • In 1913, he published a theory on atomic structure based on Rutherford’s discovery of the atomic nucleus • 1916, he became a professor at Copenhagen University, and in 1920 was appointed director of the Institute of Theoretical Physics • Was awarded the Nobel Prize in 1922 for his studies of the structure of atoms • Had a wife and six sons • Died on October 19, 1937

4. Rutherford’s Experiment • A beam of alpha particles was aimed at a sheet of gold foil • A screen coated with zinc-sulfide surrounded the foil and flashed when hit by an alpha particle • Rutherford and his team observed where the flashes were to determine if the foil deflected the alpha particles.

6. Rutherford’s Conclusions • Based on the “plum pudding” model of the atom, Rutherford expected all of the particles to pass through the gold foil and be only slightly deflected by electrons. • Instead, some particles were deflected at large angles. • Rutherford concluded that the plum pudding model was not correct. He concluded that there was a dense nucleus that contained most of the atom’s mass and positive charge.

7. Bohr’s Conclusions • Bohr proposed that electrons travel in orbits around the nucleus and that the inner orbits could hold fewer electrons than the outer orbits. • Suggested that outer orbits determine the chemical properties of the atom. • Also explained that atoms have different levels based on energy. When energy is added, the electron moves to a higher orbit. • Bohr’s ideas were the basis for quantum mechanics

8. Citations • http://nobelprize.org/nobel_prizes/chemistry/laureates/1908/rutherford-bio.html • http://nobelprize.org/nobel_prizes/physics/laureates/1922/bohr-bio.html • http://library.thinkquest.org/28582/bio/rutherford.htm • http://library.thinkquest.org/28582/bio/bohr.htm • http://www2.lucidcafe.com/lucidcafe/library/95oct/nbohr.html • http://www.windows.ucar.edu/cgi-bin/tour_def/people/modern_era/rutherford.html • Buthelezi, Thandi, Laurel Dingrando, Nicholas Hainen, Cheryl Wistrom, Dinah Zike. Chemistry: Matter and Change. New York: Glencoe, 2008.