ATOMIC THEORY

DEMOCITRUS 460-370 B.C

• Ancient greek philosopher
• Proposed the atomic theory
• Based more on philosophy than science
• Reffered to as "atomos"
• Believed they would continually divide to no end

DEMOCITRUS

DALTON 1776-1844

• Renamed the particles "atoms"
• Believed they were small round indstrucable spheres
• Each element contained different atoms
• All the atoms in an element were identical; to shape, mass and volume,etc
• Believed they combined in whole number ratios to form compunds

DALTON

THOMSON 1856-1940

• Proposed the existence of electrons
• Electricity passing through the vaccumm cylinders wouldmbend towards positively chaeged plates
• Believed that atoms contained negative charges called electrons
• Created the plum pudding model
• Large amount of empty space with electrons suspended in the sphere like area

THOMSON

RUTHERFORD 1871-1937

• Tested to find out if the atom is "empty"
• Used alpha particles to pass through gold foils
• Majority of particles passed strait through
• Small percentage boucned off or deflected
• Discovery of the nucleus, center of the atom; made up of positive particles called protons

RUTHERFORD

NEILS BOHR 1885-1962

• Danish philosopher who established the modern atomic theory
• Electrons with a negative charge traveled in orbitals around the nucleus
• Nucleus consisted of protons with a positive charge and neutrons with a neutral charge
• Farther from nucleus the more energy it had
• Electrons would switch orbit when releasing/ absorbing energy

BOHR