Rutherfords model of the Atom

1. Rutherfords model of the Atom

2. People in the group • Jordan Neil • Erin Isnor • Heather Pickford • Daniel Deines • Leanne Myers

3. Ernest Rutherford

4. Ernest Rutherford1st Baron Rutherford of Nelson and Cambridge(1871-1937) • Ernest Rutherford, British physicist, who became a Nobel laureate for his pioneering work in nuclear physics and for his theory of the structure of the atom. • Rutherford was born on August 30, 1871, in Nelson, New Zealand, and was educated at the University of New Zealand and the University of Cambridge. He was professor of physics at McGill University in Montréal, Quebec, from 1898 to 1907 and at the University of Manchester in England during the following 12 years. After 1919 he was professor of experimental physics and director of the Cavendish Laboratory at the University of Cambridge and also held a professorship, after 1920, at the Royal Institution of Great Britain in London.

5. His famous experiment In 1911 Ernest Rutherford thought it would prove interesting to bombard atoms with alpha rays, figuring that this experiment could investigate the inside of the atom (sort of like a probe). He used Radium as the source of the alpha particles and shinned them onto the atoms in gold foil. Behind the foil sat a fluorescent screen for which he could observe the alpha particles impact.

6. What was supposed to happen?

7. The results of the experiments came unexpected. Most of the alpha particles went smoothly through the foil. Only an occasional alpha veered sharply from its original path, sometimes bouncing straight back from the foil. • Rutherford reasoned that they must get scattered by tiny bits of positively charged matter. • Most of the space around these positive centers had nothing in them. He thought that the electrons must exist somewhere within this empty space.

8. Rutherford thought that the negative electrons orbited a positive center in a manner like the solar system where the planets orbit the sun.

9. What does he know.. • Rutherford knew that atoms consist of a compact positively charged nucleus, around which circulate negative electrons at a relatively large distance. • The nucleus occupies less than one thousand million millionth of the atomic volume, but contains almost all of the atom's mass. If an atom had the size of the earth, the nucleus would have the size of a football stadium.

10. What Confronted Rutherford? • Ernest Rutherford had been studying alpha particles since 1898. In fact, he discovered them. • To him, alpha particles were part of the family. In 1909 he was confronted with some rather bizarre alpha-particle behavior that he had to explain. What was the behavior, exactly?

11. Hans Geiger and Ernest Marsden aimed a stream of alpha particles at a thin gold foil for several months in 1909. (They would continue studying scattering until 1913.) Geiger cites a thickness of 8.6 x 10¯6 cm. for the foil. In fact, the foil was so thin that it had to be supported on a glass plate. (The plate without any foil was studied and no deflections were found. It was transparent to the alpha particles.) There were three major findings: