Download Atoms, Elements, and Ions

Atomic Theorists
How we got to where we are now
Law of Conservation of Mass
• Who: Antoine Lavoisier
• Matter can't be created or destroyed
• When: 1785
• Where: France
Law of Definite Proportions
• Who: Joseph Proust
• Compounds – Elements put together in
fixed ratios
C + O2  CO2
• When: 1797
• Where: France
Law of Multiple Proportions
• Who: John Dalton
• Two elements can form more than one
compound
• The ratios of the masses of the first and second
elements will be small whole numbers.
• Where: England
When: 1803
Who: Aristotle
What: All matter is a combo of fire, air, earth or water
When: 350 B.C.
Where: Greece
Who: Democritus
•When: 400 B.C.
•Where: Greece
•What: Matter was made of indivisible substances he
called atomos (1st talk of the atom)
Who: John Dalton
What: Solid Sphere Model (1st atomic theory)
•Elements are made up of indivisible particles called atoms
•Each element was composed of the same kind of atoms.
•Different elements were composed of different kinds of
atoms.
•Compounds are composed of atoms in specific ratios.
•Atoms are not created or destroyed in a reaction.
When: 1805
Where: England
Who: J.J. Thomson
What: Atoms aren't smallest particle
•Conducted experiment with a Cathode
Ray Tube
•Particles had a negative charge
(discovered electrons)
•Model = plum pudding
When: 1897 Where: England
Cathode Ray Tube
Who: Robert Millikan
What:
•Experiments to determine mass of electron
•Conducted the oil drop experiment
•Verified that electron is negatively charged
•No new model
Where: America
When: 1910
Millikan
Oil Drop Experiment
Who: Ernest Rutherford
What:
• Conducted Gold Foil experiment
• Proved nucleus is dense, positively charged core of
atom
Model = Planetary Model
• When: 1911
• Where: America
Rutherford’s Experiment
Gold Foil Experiment
Results of
foil
experiment
if Plum
Pudding
model had
been
correct.
What Actually Happened
Who: Niels Bohr
• What: Pulsating Planetary Model
• Electrons can move between energy levels
• When: 1913
• Where: Denmark
Bohr Model Energy Levels
Who: Erwin Schrodinger
• Electron have dual wave-particle nature
• Foundation for quantum theory
• Model = Pulsating orbitals
• Math was used to predict path of the electron
• When: 1926
• Where: Switzerland
Who: James Chadwick
What:
• Confirmed existence of neutron
• No new atomic model
• When: 1932
• Where: England