Democritus - 429 B.C.First person to think of the atom. The atom was a solid cirlce.
Aristotle - 400 B.C.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 NewtonTiny pieces of mass. His model was a solid circle.
John Dalton- 1766-1844 (Theory dev. in 1803)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 BecquerelDiscovered radioactivity
JJ ThomsonDiscovered electrons
Model: Cirlce containing negatively charged electrons and positively charged protons
Cathode Ray Tube
MillikanMeasured charge and mass of an electron
Model: negatively charged electrons and a large cross through the center
RutherfordAtom has a central positive nucleus surrounded by nagative orbiting electrons
Model: negatively charged electrons surrounding a positive nucleus
Niels Bohrelectrons in orbit
positively charged nucleus Model contains 3 rings and a dot in the middle
discovered isotopes Model: 2 rings and a colored in circle in the middle
Atom consists of clouds and nucleus
Calculated odds of where an electron might be
Proved Bohr wrong
James ChadwickDiscovered the neutron Model: vertical and horizontal rings connected through the center