Chemistry

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