Across
- 2. time for one-half atom to decay
- 3. positive charge
- 5. an atom that is radioactive
- 10. neutral charge
- 12. protons+neutrons
- 13. one of the several forms of the same element substance that cannot be decomposed
Down
- 1. capable of releasing radiation
- 4. unit of matter and energy
- 6. group of atoms
- 7. negative charge
- 8. representing a particular isotope
- 9. how much space something takes up
- 11. the weight
- 12. no electric charge