Audrey Ferguson

Democritus - 429 B.C.

101

First person to think of the atom. The atom was a solid cirlce.

Aristotle - 400 B.C.

101

He discoverd the four elements of life: air, wind, water, fire. His model was a diamond dividing the elements into it's corners.

Sir Isaac Newton

Oct 7, 1704

Tiny pieces of mass. His model was a solid circle.

John Dalton- 1766-1844 (Theory dev. in 1803)

Oct 7, 1766

Dalton's Atomic Theory.
All matter is composed of atoms (T)
Atoms can't be made or destroyed (F)
Atoms of same elements are identical (T)
Different elements=different atoms (T)
Model: circle (not filled in)
Chemical reactions occur when atoms are rearranged (F)
Compounds are formed from atoms of different elements (T)

Henri Becquerel

Oct 7, 1896

Discovered radioactivity
Model:solid circle

JJ Thomson

Oct 7, 1897

Discovered electrons
Model: Cirlce containing negatively charged electrons and positively charged protons
Cathode Ray Tube

Millikan

Oct 7, 1908

Measured charge and mass of an electron
Model: negatively charged electrons and a large cross through the center

Rutherford

Oct 7, 1911

Atom has a central positive nucleus surrounded by nagative orbiting electrons
Model: negatively charged electrons surrounding a positive nucleus

Niels Bohr

Oct 7, 1913

electrons in orbit
positively charged nucleus Model contains 3 rings and a dot in the middle

Aston

Oct 7, 1920

mass spectrometer
discovered isotopes Model: 2 rings and a colored in circle in the middle

Shrodinger

Oct 7, 1926

Atomic Model
Atom consists of clouds and nucleus
Discovered formula
Calculated odds of where an electron might be
Proved Bohr wrong

James Chadwick

Oct 7, 1932

Discovered the neutron Model: vertical and horizontal rings connected through the center