Models of the Atom

J.J. Thomson discovered the electron using

• gold foil and alpha particles.

• oil drops.

• a cathode ray tube.

• emission spectra of a hydrogen atom.

Rutherford realized that the atomic nucleus was positively charged because

• it attracted alpha particles.

• it deflected alpha particles.

• it had no effect on alpha particles.

• it produced alpha particles.

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Niels Bohr added _______________ to the model of the atom.

• electrons.

• a nucleus.

• neutrons.

• energy levels.

Alpha particles have a charge of +2 and a mass of four atomic mass units (amu). Because the mass was greater than the charge, James Chadwick concluded that atoms contain

• a nucleus.

• positive material in which electrons are embedded.

• neutrons.

• negative particles that cancel part of the positive charge.

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Which of the following is the best evidence that the particles that make up a cathode ray had a negative charge?

• The particles were produced by many different metals.

• The ray was deflected toward a positive electric field.

• Line emission spectra for an element are always the same.

• The ray caused a phosphorescent screen to glow.

How many energy levels would be in the Bohr model for magnesium?

• 1

• 2

• 3

• 4

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J.J. Thomson discovered electrons, and he also knew that atoms are neutral. From these two facts, Thomson inferred that the atom also contains

• positive material.

• a nucleus.

• neutrons.

• energy levels.

If an atom were enlarged so that the nucleus were the size of a marble, then the entire atom would occupy the volume of a(n)

• tennis ball.

• basketball.

• large beach ball.

• football field.

Which of the following is the best description of J.J. Thomson's model of the atom?

• a featureless, indivisible sphere

• a sphere of positive material with electrons embedded in it

• mostly empty space with electrons randomly orbiting around a positive nucleus

• mostly empty space with electrons located in set orbits around a positive nucleus.

A line emission spectrum is produced when electrons

• become excited and move from ground state to higher levels in an atom.

• leave the atom completely.

• fall from higher, excited states back to lower or ground state.

• move from a cathode to an anode.

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