ATOMIC THEORY TIMELINE

DEMOCRITUS

• a Greek philosopher
• stated that nothing exists except for atoms and empty space.
• "Nothing exists except for atoms and empty space; everything else is opinion."
• -Democritus

DALTON'S ATOMIC THEORY

• each element is composed of indestructable, small particles called atoms.
• all atoms of an element are identical
• -they have the same mass, volume, and other physical/ chemical properties
• atoms combine in whole number ratios to form compounds
• atoms are untreatable, so they have to combine as whole atoms

J.J. THOMSON

• made the plum pudding model
• the atom is unbreakable
• the atoms structure has electrons suspended in a positively charged electric field

RUTHERFORD

• developed the theory of an atom's structure
• conductuped an experiment with gold foil
• he observed the alpha particles
• during this experiment found that there is a small, dense center in the middle of an atom
• this is the nucleus, which is positively charged

BOHR ATOMIC MODEL

• electrons travel in orbits around the nucleus
• the farther the electron is from the nucleus, the more energy it has
• his model only works with atoms with one electron, hydrogen

ERWIN SCHRÖDINGER

• the quantum mechanical model of the atom
• found the equation that predicts the probability of finding an electron
• with a certain amount of energy in a certain area in an atom