Download Development of Atomic Theory: Democritus to Thomson

Name: _________________________ Period: ___
Development of Atomic Theory
Do ideas or theories in Science stay the
same? What causes this?
 ________________________________
 ________________________________
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1. Who was Democritus?
2. What did he conclude?
What does the Greek word atomos”
mean?
What is our modern definition of the
atom?
In the late 1700’s a British chemist and
schoolteacher, John Dalton, brought
back Democritus’s idea of the atom.
What 3 ideas did his new theory of the
atom propose?
In 1897 a British scientist named
Thomson discovered that atoms were
not indivisible but were made up of
smaller particles. What particle did
Thomson discover and what
electrical charge does it have?
1. _________________________________
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2. _________________________________
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3. _________________________________
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The particle Thomson discovered was the ____________.
It has a ___________charge.
In 1909 a former student of
Thomson’s, Ernest Rutherford
decided to test the idea that
1. ______________________
electrons are evenly distributed
2.
throughout the atom. What did he
3. ______________________
discover and where was it located?
Bohr’s Model suggests:
Bohr suggests that ___________________ are only found in
specific orbits around the _______________.
The cloud model modified Scientists determined that _______________ do not orbit the
Bohr’s model and said:
_____________ like planets. Instead, they move rapidly within a
________________ region.
James Chadwick
discovered what and why
was it hard to find?
1. _____________
2. ________________________________________
_______________________________________.