1 Chemistry Notes – History of the Atom
I.
Democritus
A.
Greek Philosopher
B.
Major Contribution: _______________________
1. He proposed that everything was made of these atoms,
and they were all ________________________
C.
Was this theory correct? _________ Why?
II. John Dalton
A.
Major Contribution: _______________________
B.
Included four principles:
1. ______________________ are composed of _________________________
particles called __________
2. All atoms of a given element are ______________________
3. _______________________ are composed of atoms of one or more elements, and will
form only in _____________________________________________
a)
This is called the Law of _________________________________________
b)
For example: _____________ exists, while ____________ does not
4. A chemical reaction involves the combination, separation, or rearrangement of
atoms, not their ____________________ or _____________________
a)
C.
This is called the Law of __________________________________________
Was this theory correct? ________ Why?
III. J.J. Thomson
A.
Major Contribution: _________________________
2 Chemistry Notes – History of the Atom
B.
Cathode Ray Tube Experiment
C.
Thomson’s Atomic Model:
1. Referred to as the ___________ ____________________ model.
D.
Was this theory correct? ________ Why?
IV. Ernest Rutherford
A.
Two Major Contributions:
1. ______________________________
2. The atom is mostly ______________________________
B.
Gold Foil Experiment
3 Chemistry Notes – History of the Atom
V.
C.
Rutherford’s Atomic Model:
D.
Was this theory correct? ________ Why?
Niels Bohr
A.
Major Contribution: _______________________________
B.
Atomic Light Spectra
1. Bohr observed that when light was given off from an atom, there were only single
lines visible
2. Bohr proposed that each line represented an electron in a different _____________
C.
Bohr’s Atomic Model:
4 Chemistry Notes – History of the Atom
VI. Current Atomic Theory
A.
Many scientists contributed to developing ______________________
_____________________ , which is the current model of the atom
B.
Known as the _____________________ _________________ model
1. The cloud is an area of ____________________________ where the electron is
2. These electrons, moving at extremely high speeds, effectively occupy the entire
area of the cloud, the same way that moving fan blades effectively occupy the entire
area through which they pass.
C.
Current Atomic Model: