Atomic Model

Democritus

460

The first to come up with the idea of the atom

Lavoisier

Aug 26, 1743

law of conservation of mass - the mass of a closed system will remain constant, dispite of the processes happening inside the system.

Dalton

Sep 6, 1766

Atomic Theory - matter is composed of discrete units called atoms

Becquerel

Apr 22, 1852

the discovery of radiation through x-rays

Thomson

Dec 18, 1856

Plum Pudding Model - If an atom is positive its electrons are negitive
Cathode Ray Tube Experiment - It is the discovery that the structure of the atom consists of negatively charged particles swimming in a sea of positive charge.

Curie

Nov 7, 1867

Thorium - slightly radioactive metel a posible replacment for uranium in nuclear power

Millikan

Mar 22, 1868

Oil Drop experiment - mesured the charge of a single electron

Proust

Jul 10, 1871

law of definite proportions - all compounds contained elements in certain definite proportions

Rutherford

Aug 30, 1871

Electron cloud model - determines the positions of electrons in an atom
Planetary model of the atom - all the protons and electrons in the nucleus orbit around the nucleus
Rutherford's nuclear atom - mass is contained in nucleus, electrons fill nearly all the atom's volume, the number electrons equals the atomic number, and the positive charge on the nucleus is equal in magnitude to the negative charge of the electrons
Gold foil experiment -the mass of the atom is in nucleous rest empty space

Moseley

Nov 23, 1887

discovery of the atomic number

Chadwick

Oct 20, 1891

discovery of nutrons

Bohr

Oct 7, 1962

Indivisible, solid sphere model - electrons can only
orbit the nucleus in continually growing orbits around the nucleus. The orbits that are the furthest out can hold more electrons. The electrons that are the furthest out determine the properties of the atom.

Crookes

Apr 22, 2009

discovery of the element Thallium