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Chapter 4- Section 1: The Development of the Atomic Theory
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Scientist/Theorist
Democritus
Dalton
Thomson
Rutherford
Bohr
Picture of Model
Description of Model
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*Proposed that atoms exist
and called them “atomos.”
*Proposed that these
atomos were eternal and
can’t be divided
*He had not scientific
evidence to support theory
*Evidence found through
experimentation
*Proposed that atoms
cannot be divided, all atoms
on an element are similar,
and elements can combine
to form compounds.
*Proposed atoms were tiny
spheres.
*Performed experiments to
suggest atoms could be
divided.
*Used cathode rays to
discover electrons.
*Proposed the plum pudding
model.
*Performed experiments to
determine structure of
atom: he shot alpha particles
(+ charge) at gold foil and
found two things:
1. Atoms have a lot of
empty space.
2. Atoms have a positively
charged center (nucleus)
*Proposed a model that had
nucleus in center of atom
with electrons orbiting
around the outside.
*Proposed planetary model
of atom in which the energy
of the electron is related to
its path around the nucleus.
Model of the Atom
1. All matter consists of invisible particles
called atoms.
2. Atoms are indestructible.
3. Atoms are solid but invisible.
4. Atoms are homogenous.
5. Atoms differ in size, shape, mass, position,
and arrangement.