Jackson and Kayla,

Ernest Rutherford
19 06 considered the father of nuclear physics
Wo n the 1908 Nobel Prize in Chemistry
Wa nted to see if Thomson's model of the atom was correct......
Se t up an experiment that fired fast moving positively charged bits of matter (alpha particles) at a thin piece of a metal such as gold.
Alpha partices come from unstable atoms. They are positively charged, and so they are repelled by particles of matter which have a positive charge (opposites attract, like repell).
Rutherford hypothesized that the gold film did not contain enough matter to stop the speeding alpha particle or change its path...........

T he unexpected results of the experiment caused Rutherford to realize that
Thomson's model was incorrect, and he proposed his own model.
Ru therford's model included a nucleus in the atom.
The positively charged proton is located in the very small space at the center of an atom.
Most of the atom is empty space occupied by nearly massless electrons.
Electrically neutral particles, neutrons are also located in the nucleus.
Th e number of electrons equal the number of protons in an atom.

A mystery of the nature of the nucleus remained unsolved.
The nucleus contains most of the atom's mass as well as the positive charge. The protons supposedly accounted for this mass.
However, a nucleus with twice the charge of another should have twice the number of protons and twice the mass. But this did not prove correct.
Rutherford speculated in 1920 that there existed electrically neutral particles with the protons that make up the missing mass but no one accepted his idea at the time.

Niels Bohr was born in Copenhagen on October 7, 1885.
He was a Danish physicist, who was awarded the
Nobel Prize in Physics 1922 for his services in the investigation of the structure of atoms and of the radiation emanating from them".
Earlier in 1910, Niels Bohr married Margrethe Norlund.
The had six sons, the oldest died in a boating accident and another died from childhood meningitis.

During World War II Bohr, fearing arrest by the Germans, escaped to Britain from where he went to the US to work on the
Manhattan Project at the Los Alamos laboratory in New Mexico. The Manhattan
Project lead to the development of the first atom bomb.
Following the war Bohr returned to
Copenhagen and worked for the peaceful use of nuclear energy.
When he was awarded the Order of the
Elephant by the Danish government, he designed his own coat of arms which featured a taijitu (symbol of yin and yang).
He died in 1962.

1913
E
This model introduced by Bohr in 1913, was a radical departure from earlier models and showed the atom with a small nucleus surrounded by electrons that travel in circular orbits in a structure similar to the solar system, with electrostatic forces providing attraction, not gravity.

1932
He found it to measure slightly heavier than the proton with a mass of 1840 electrons and with no charge (neutral). The proton-neutron together, received the name,
"nucleon".

For four years, James Chadwick was a prisoner of war in Germany. When World
War I ended, he returned to his native England to rejoin the mentor of his undergraduate days, Ernest Rutherford.
Chadwick kept the problem of the Rutherfords's model of the atom in the back of his mind while working on other things.
Chadwick repeated experiments that Marie Curie's daughter had been working on, but with the goal of looking for a neutral particle -- one with the same mass as a proton, but with zero charge. His experiments were successful.
He was able to determine that the neutron did exist and that its mass was about 0.1 percent more than the proton's. He published his findings with characteristic modesty in a first paper entitled "Possible Existence of Neutron." In 1935 he received the Nobel Prize for his discovery.

Although scientists knew that atoms of a particular element have the same number of protons, they discovered that some of these atoms have slightly different masses.
They concluded that the variations in mass result, more or less, from the number of neutrons in the nucleus of the atom.
Atoms of an element having the same atomic number but different atomic masses get called "isotopes" of that element.

Nuclear Power First atomic bomb-1945

The science of atomic radiation, atomic change and nuclear fission was developed from 1895 to 1945, much of it in the last six of those years.
Ov er 1939-45, most development was focused on the atomic bomb.
F rom 1945 attention was given to harnessing this energy in a controlled fashion for naval propulsion and for making electricity.
Sin ce 1956 the prime focus has been on the technological evolution of reliable nuclear power plants.
Uranium was discovered in 1789 by Martin Klaproth, a German chemist, and named after the planet Uranus.

Your assignment is to finish filling out the Study Guide from your reading the Atomic
Theory Handout from the science site.
Re ad the material again if needed. Write out paragraphs on Rutherford, Chadwich,
Schrodinger, Bohr and atomic energy.
Us e your flash cards/ Element test is Dec. 15th, Monday.
THIS SHOULD ALL BE DONE FOR
THURSDAY'S CLASS!