atommmmmmmmm

Democritus

370

First to think or make model of an atom!
sadly, all his books were burned.

John Dalton

Jan 1, 1802

He performed experiments that proved Democritus' theory true! :)
Daltons Atomic Theory
-all matter is composed of atoms. (true)
-atoms cannot be made or destroyed.(false)
-all atoms of same element are identical. (false)
-different elements have different types of atoms. (true)
-chemical reactions occur when atoms are rearranged. (true)

J.J. Thomson

Jan 1, 1897

"Plum pudding model"
-first to measure the electron
-developed plum pudding model of the atom. Described the atom as a slightly positive with small electrons.

R.A. Millikan

Sep 19, 1909

found mass and charge of electrons. He used "oil drop" experiment.

Ernie Rutherford

Sep 19, 1911

"Atoms have a positive nucleus." electrons are far away, circulating the nucleus. Nucleus is really tiny, but very dense. Called out "protons"
*Used gold foil experiment (which was firing particles at gold atoms and measuring their deflections)

Nieis Bohr

Jan 19, 1913

Created Bohr model, asked to make it by Rutherford who wasn't sure about his model.

EINSTEIN

Sep 19, 1913

able to determine the size of atoms@

Parsons Theory

Sep 19, 1915

Anti-Bohrs model, but not enough evidence to prove. Some believe it still today!

Sommerfied

Jan 19, 1920

expanded Bohrs model to show that electron don't always rotate on circular rings.

Erwin Shroedinger

Sep 19, 1920

Created the cloud model. Describes a cloud-like region where the electron numbers most likely found.

James Chadwick

Sep 19, 1932

Found nuetron, which is the same mass as a proton