4th Nine Weeks Bonus Crossword Puzzle

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Across
  1. 2. A microscopic particle that makes up all matter.
  2. 3. Number 1 on the periodic table.
  3. 6. The atoms on the 18th column of the periodic table.
  4. 8. Substance with a pH greater than 7
  5. 10. The time required for a certain amount of atoms to decay by half the amount originally present.
  6. 13. A temperature measuring instrument.
  7. 15. Substance with a pH less than 7
  8. 16. A combination of 2 or more substances
  9. 17. A positively charged ion.
  10. 20. KHDUDCM
Down
  1. 1. A positively charged particle.
  2. 2. A negatively charged ion.
  3. 4. A particle with no charge.
  4. 5. A substance's mass per unit of volume (Water's is 1 gram per millimeter.)
  5. 7. Light particle.
  6. 9. A negatively charged particle.
  7. 11. The phase state of H2O when it is ice
  8. 12. Rings around atoms that hold electrons.
  9. 14. the outermost electrons of an atom.
  10. 18. One measurement of this is 6.02 x 10^23 units of a substance.
  11. 19. The phase state of H2O when it is vapor
  12. 21. The center of an atom.