SCIENTISTS

DEMOCRITUS

ATOMOS MODEL

• Democritus coined the term "atom"
• He discovered atoms were the smallest block of life
• He believed atoms had hooks on them so they could combine

ARISTOTLE

EARTH, FIRE, WATER, AIR

• Aristotle thought Democritus was wrong
• He believed that all things were made of the four elements
• He was wrong about this point,
• Defending the idea that the earth was the center of the universe

DALTON

BILLIARD BALL MODEL

• Dalton believed that atoms were solid, with no smaller components
• He worked with gases and made a revolutionary discovery
• He found that elements can only be combined in certain ratios

JJ THOMSON

PLUM PUDDING MODEL

• Thomson is famous for his idea that atoms are like plum pudding
• He discovered electrons using a cathode ray
• This overthrew the theory that atoms were the smallest thing

MILLIKAN

MASS/CHARGE OF ELECTRON

• Millikan used his oil drop experiment to make a great discovery
• He found the charge of electrons
• Because the ratio of charge to mass was known, he also found the mass

RUTHERFORD

POSITIVELY CHARGED NUCLEUS MODEL

• Rutherford's famous gold foil experiment
• He fired atoms at foil, and most came straight out the other side
• Every once in a while, though, a particle would bounce straight back
• Rutherford had found the nucleus

CHADWICK

PROTON NEUTRON MODEL

• Why was atomic mass larger than atomic number?
• Protons and electrons couldn't be the only particles...
• Chadwick discovered neutrons