periodic table

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Across
  1. 2. a group of atoms bonded togethe
  2. 4. protons in the nucleus of an atom,
  3. 8. surrounding the nucleus of an atom.
  4. 9. mass of an atom
  5. 10. charge of negative electricity
Down
  1. 1. essential or characteristic.
  2. 3. positive electric charge
  3. 5. wo or more forms of the same element
  4. 6. same mass as a proton
  5. 7. the basic unit of a chemical element.