1. SC-100 Class 13 Review Questions
1. One difference between the motion of electrons in an atom and the motion of planets in the solar systems is that
a. gravity holds the planets in orbit while centripetal force holds the electrons.
b. planetary orbits are quantized, electron orbits are not.
c. Brownian motion applies to planets but not electrons.
d. planets can change their orbits and electrons cannot.
e. All of the above apply to both planets and electrons.

2. SC-100 Class 13 Review Questions
2. Materials made from a single type of atom that cannot be broken down any further are called
a. atoms.
b. elements.
c. molecules.
d. solutions.
e. compounds.

3. SC-100 Class 13 Review Questions
3. The fundamental building block for all matter; the smallest representative sample of a substance that maintains chemical identity.
a. atom
b. element
c. molecule
d. electron
e. compound

4. SC-100 Class 13 Review Questions
4. We know that atoms have a nucleus because
a. alpha particles exist.
b. this is a necessary philosophical consequence of the requirement that there be change in the world.
c. the Rutherford experiment on the scattering of alpha particles from gold gives evidence for it.
d. there are no isolated monopoles in nature.
e. None of the above are evidence for the existence of the nucleus.

5. SC-100 Class 13 Review Questions
5. Electrons in the Bohr atom shift to a higher energy level by
a. absorbing the energy of light or heat.
b. reflecting the energy of heat or light.
c. emitting a photon.
d. producing an individual electromagnetic wave.
e. Electrons in the Bohr atom cannot change energy states.

6. SC-100 Class 13 Review Questions
6. Each electron shell corresponds to a different
a. electron.
b. element.
c. ion.
d. atom.
e. energy level.

7. SC-100 Class 13 Review Questions
7. If an electron moves from a higher energy shell to a lower energy shell
a. a photon is emitted.
b. a photon is absorbed.
c. an observer will see light.
d. the electron disappears between shells.
e. a & c & d

8. SC-100 Class 13 Review Questions
8. In the periodic table of the elements, the atomic number equals
a. the number of protons in the nucleus.
b. the number of neutrons in the nucleus.
c. the number of electrons in the outer shell.
d. the mass of the atom.
e. the mass of the photon.