Atomic Model Timeline

Democritus

150

Democritus lived from around the time of 500B.C.. His theory was that all matter consisted of really tiny small particles that couldn't be split apart.

Aristotle

210

Aristotle believed that there wasn't a fixed amount to the number of times that matter could be split apart.

Isaac Newton

Jan 1, 1704

Newton came up with the idea that atoms were held together by some kind of attraction or force.

John Dalton

Mar 13, 1802

John Dalton's theory was that all matter is made up of tiny particles that couldn't be divided. Explanations- 1.) That every atom will contain atoms. 2.) All atoms that make the element will always weigh the same and then the atoms of others elements would have a different weight. 3.) All compounds will contain atoms of more than one element. 4.) In some compounds the atoms of different elements will always combine in the same way.

J. J. Thomson

Aug 21, 1897

In 1897 J.J. Thomson discovered that atoms were made of even smaller particles that are called electrons. Thomson put a pair of charged plates on oth sides of a glass tube. The plates then caused the beam to bend instead of staying on a straight path. Thomson then saw that the beam was pushed back by the negative charges and that they were attracted by the positively charged plates.

Hantaro Nagaoka

Sep 27, 1904

Hanataro made a modelof an atom that was based from the rings of Saturn. From the model came 2 predictions. 1.) There is a very large nucleus. 2.) There are electrons that go around the nucleus that are connected by an electrostatic force.

Ernest Marsden

Oct 31, 1909

Ernest Marsden lived from 1889-1970. He helped Ernest Rutherford with his Gold Foil Expierment. He told Rutherford his observation of the expierment. He said that the largest particle that came from a radioactive source were often reflected more than 90 degrees.

Ernest Rutherford

Oct 30, 1911

Rutherford's hypothesis was that gold would be to small to change the direction that the largest particle would be moving in. His prediction was that most of the particles would travel in a stright path from the source to a screen that was lit up when struck by the particles. More particles were curved more than Rutherford had thought would have.

Niels Bohr

Dec 15, 1913

In Bohr's model the electrons moved. They orbitted around the nucleus kinda of like planets. He used the work of other scientists that helped him prove his theory. A scientist that he learned from was Albert Einstein.

Louis de Broglie

Oct 30, 1924

Came up with th idea that particles that move some like electrons have what are called waves. This showed that articles didn't move in an orbical attern like th solar system.

Erwin Schrodinger

Oct 30, 1926

Erwin Schrodinger used math equations to prove how the motion in atoms worked.

James Chadwick

Oct 30, 1932

Had the discovery of the neutron he found out that neutrons had no charge at all. But a nuclei contained neutrons that have positively charged protons.

Lise Meitner

Oct 31, 1939

Lise Meithner was known for her prediction of a possible chain reaction in an atom. Which would lead to the creation of the atomic bomb. She used Neils Bohr's work to prove her reasoning.