-
340
Aristole
Born 384-322 B.C.E.
He did not believe in the atomic theory by Democritus.
He believed all materials on earth were formed by water, earth, fire, and air. Which was over looked for 200 years. -
400
Democritus
Born from 460-370 B.C.E.
His belief was that matter was ultimatley composed of small invisible particles. Also suggested that if you break up matter you will eventually get a tiny industructable atom.
This belief was not widely accepted. -
Dalton
From 1803-1808 Daltons atomic theory consisted of 3 major parts:
1. An element is composed of tiny indestructable particles called atoms
2. All atoms of a given element have the same mass and other properties that distinguish them from atoms of other elements
3. Atoms can combine in simple ratios to form compounds -
Mendeleev
in 1869, he noticed that certain groups of elements had similiar properties.
Listed the order of elements by increasing mass, and also realized that the similiar properties formed a pattern (Periodic Law) -
Thomson
Believed negatively charged electrons were small particles held within a positively charged sphere ( Plum pudding experiment)
He discovered the electron -
Ferdinand Brown
Cathode ray tube-to see how the electrons and protons would be moving -
Rutherford
Born (1871-1937)
He performed experiement to confirm Thomsons theory.
Proved Thomsons plum pudding experiment to be wrong.
He performed the gold foil experiment -
Bohr
Born 1885-1915
quantized shell model of atom.
same year worked for Rutherford on the elctron theory of matals -
Mosley
Born 1885-1915
He found a link to the atomic number by x-ray (Quantum theory) -
Millikan
Born 1868-1953
The measurment of the elementary electronic charge and for his work on the photoelectric effect -
Schrodinger
quantum mechanical year (1887-1961) assigned to rutherfords (alpha particles) (gamma radiation) -
Chadwick
Born 1891-1974
Discovered the neutron
