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Atomic Theories and Models
Atom:
Atomic Theory:
Theory
John Dalton
Year:
His atomic model stated that:
1)
2)
3)
4)
Michael Faraday
Year:
- Discovered atoms can gain electric charges and
form charged atoms called _________
- In this modified version of Dalton’s model, he said:
1)
2)
3)
Model
Analogy
J.J. Thomson
Year:
- His “raisin bun” model explained:
1) Atoms contain particles called
_____________________
2) Electrons have a small mass and __________ charge
3) The rest of the atom is a sphere of ____________
charge
4) The electrons are embedded in this sphere, so
that the resulting atoms are ________________ or
uncharged.
H. Nagaoka
Year:
- Modeled the atom as a large _________________
sphere surrounded by a ring of negative
__________________
- He did not talk about protons or neutrons
Ernest Rutherford
Year:
- He tested Thomson’s and Nagaoka’s models by aiming
alpha particles at a thin sheet of gold foil. He thought the
particles would all pass through but a very small amount
bounced straight back.
- To explain his results, he came up with the nuclear
model:
1) An atom has a tiny, dense, positive core called the
_____________ (which deflected the alpha particles
and contains ___________________)
2) The nucleus is surrounded mostly by empty
space, containing rapidly moving negative
___________________ (through which the alpha
particles passed through)
Niels Bohr
Year:
- He developed this model to explain where the electrons
go around the nucleus.
- In his diagrams, the symbol of the element is written in
the center to represent the nucleus
- A series of circles is drawn around the nucleus to
represent the orbits, and electrons are shown in these
orbits
Bohr-Rutherford Diagrams
- a combination of Rutherford’s nuclear model with
Bohr’s planetary model
- it summarizes the numbers and positions of all
three subatomic particles in an atom
- a circle is drawn in the center to represent the
nucleus. The numbers of protons and neutrons are
written in this circle
- electrons are again shown in circular orbits around
the nucleus