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WHS  H Chemistry
H Practice Problems Ch.4 & 25
1. Smallest particle of an element that retains all properties of
that element.
2. Democritus thought that all matter consisted of very small
indivisible particles which he named atomos, and today we
know that there are particles smaller than an atom
3. Dalton said that atoms of the same element are identical,
which today we know is not true (isotopes/ions); and that
atoms can’t be subdivided, created or destroyed, but the
process fission and Fusion subdivide atoms
4. Since the ray is bent towards (attracted to) the positive plate and away (repelled) from the
negative plate you can conclude that the ray is negative.
5.
Proton Neutron Electron
Symbol
Charge
𝑝+
+1
𝑛0
0
Location
nucleus
nucleus
Relative
Size
(mass)
1
1
𝑒−
-1
outside
nucleus
0
6.
Rutherford expected that the positive alpha
particles would pass right through the gold foil
because the atoms making up the gold foil were
thought to be a diffuse positive mass with negative
particles evenly distributed throughout (JJ
Thomson’s plumb pudding model).
7.
The large deflection angles some alpha
particles made.
8. The atomic theory that Rutherford proposed after the results of his gold foil experiment consisted
of an atom with a small dense positive center and mostly empty space.
9. Rutherford’s Atomic Model (Nuclear Model)
Thomson’s Atomic Model (Plum Pudding Model)
10. Bohr said that the electrons were not only located outside of the nucleus, but orbited the nucleus
in circular orbits, like planets orbiting the sun (hence planetary model)
11. Schrödinger viewed electrons as dense clouds of various shapes surrounding the nucleus, each
with a different probability of possessing an electron.
12. The number of protons in an atom distinguishes it from an atom of a different element. It is
represented on the periodic table as the atomic number.
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