Across
- 2. two atoms with different numbers of neutrons
- 5. equal to the number of protons plus neutrons
- 7. an electron in the outermost energy level of an atom.
- 9. Tiny very light particles have a negative electrical charge
Down
- 1. atom that carries an electrical charge
- 3. Much larger and heavier than electrons, have a + charge
- 4. average mass of the naturally occurring isotopes of an element
- 6. any of the possible energies an electron may have in an atom.
- 8. number of protons in an element