Across
- 2. two atoms with different numbers of neutrons are called.
- 4. have a positive charge (+).
- 6. an electron in the outermost energy level of an atom.
- 8. have no electrical charge.
- 9. is a cloud around the nucleus.
- 10. any of the possible energies an electron may have in an atom.
Down
- 1. number of protons.
- 3. equal to the number of protons plus neutrons.
- 5. have a negative electrical charge (-).
- 7. average mass of the naturally occurring isotopes of an element.