Download The Rutherford Model

Chemistry 1 Academic
Name: ______________________________
The Rutherford Model
Date: _______________________________
24 Points
Block/Day: __________________________
In order to study the atom, which is too small to see, Rutherford used radiation from the element
_____________________. Rutherford encased the polonium in a lead box with a hole. The rays
hit a fluorescent screen that lit up upon impact. A strong magnetic field bent one set of rays in
one direction and another set strongly in another direction, which showed the particles had
_____________and ________________. Rutherford called them alpha and beta particles.
The alpha particle was fast, massive and ________________ charged. Rutherford selected it to
probe the atom and penetrate into the atom. Rutherford used a point source of alpha particles, a
piece of ____________ foil and a zinc sulfide detection screen. Most of the particles passed
straight through the gold foil, but occasionally a particle was deflected. More rarely a particle
had a direct __________________________.
Rutherford was so surprised by the findings he compared the likelihood to firing a naval shell into
a piece of __________________ paper and having bounce back and hit you.
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Rutherford concluded the gold foil at the atomic level be must mostly ______________ ________.
What causes the deflections and rebounds? One possibility was a collision, like when two
billiard balls ___________________. A collision creates a distinct scattering pattern. NOTE THE
SCATTERING PATTERN! Rutherford placed the screen at many locations to track the particles
until he got a pattern of the scattering. This pattern was quite different then the
______________________ of the billiard ball collisions. NOTE THE COMPARSION OF THE
SCATTERING PATTERNS!
Rutherford looked to __________________________ Law for an explanation. The force of
repulsion between two particles with the same charge increases as the distance between them
decreases. Rutherford wondered if it was possible that the alpha particle was encountering a
positively charged __________________ in the gold foil?
When an alpha particle is on a direct collision course with a positive nucleus, approaches the
nucleus, it _______________ _______________, stops then reverses direction. An alpha particle
with a path that takes it
just alongside the nucleus will have both its speed and direction changed. The force from the
nucleus can be broken down into component vectors. The force _______________ to the alpha
particle slows it down, and the force perpendicular to the alpha particle changes its direction.
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A characteristic curve is traced when one charged ________________ passes another. By
assuming a charged nucleus, Rutherford mathematically calculated a scattering pattern that
matched the pattern in his _____________
____________________ experiment.
Rutherford knew that the closer the alpha particle was to the nucleus the greater the __________
of deflection. He was able to determine the distance of closest approach to the nucleus that
indicated the nucleus was no larger than 3 x 10-14m. The atom is ________________ by
comparison at 1.0 x 10-10 m.
Rutherford coined the term ___________________ for this tiny central core.
He proposed a structure for the atom that mimics in miniature the _____________
___________.
The tiny heavy nucleus is orbited by lighter electrons. The force of attraction between the
nucleus and the electrons keep the electrons from flying off into _________________, but it is not
great enough to pull the orbiting electron into the nucleus.
Although his model was a significant step forward, there were problems. Classical physics says
a charged particle in motion gives off electromagnetic radiation, a form of __________________.
An electron moving in a circle is an accelerating charge. If the electron is giving off energy, it is
also losing that energy. This should cause the electron to move closer to the nucleus where it
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will ____________________ more frequently, thus increasing the frequency of the radiation. This
kind of frequency shift is _________________ observed. Eventually the electron would lose so
much energy it would spiral into the nucleus. But in reality, most atoms are very _____________.
The Rutherford model, if it was to survive needed help urgently.
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