chemistry

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Across
  1. 5. has a negative charge
  2. 7. formed when atoms combine
  3. 8. smallest piece of an element
  4. 9. vertical columns of the periodic table
  5. 10. center part of an atom
  6. 12. abbreviations for the names of elements
Down
  1. 1. mass number of protons plus neutrons
  2. 2. has a positive charge
  3. 3. horizontal rows of the periodic table
  4. 4. an atom that has gained or lost electrons
  5. 6. has no charge
  6. 11. molecules formed from two or more different elements