Transcript Unit 2 Atomic Theorists PPT

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 of small whole
numbers
C + O2  CO2
• When: 1797
• Where: France
Law of Multiple Proportions
• Who: John Dalton
• Two elements can form more than one compound
• The subscripts of the elements in the compounds
will be small whole numbers.
» C + O2  CO2
» C + O2  CO
• Where: England
When: 1803
Who: Aristotle
What: All matter is a combination 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
Problems with Dalton’s Theory Today
(issues that weren’t known about ..yet)
1. Matter is composed of indivisible particles
There are electrons, protons and neutrons
2. All atoms of a particular element are
identical
There are isotopes
3. Different elements have different atoms
4. Atoms combine in whole number ratios
5. Atoms can’t be created or destroyed
Nuclear explosions destroy matter
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;
1.6 x 10 -19 coulombs
•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 = Stationary Planetary
• 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
There were many people involved
with developing the mathematical
process to determine the path of the
electron. One of these men was
Schroedinger.
What: pulsating orbital model
When: 1926
Where: Switzerland
Who: James Chadwick
What:
• Confirmed existence of neutron
• No new atomic model
• When: 1932
• Where: England