Parts of an Atom

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Across
  1. 2. Abbreviations used for elements
  2. 3. Negative charge in an atom's nucleus
  3. 5. The mass of an atom of a chemical element
  4. 6. Neutral charge in an atom's nucleus
Down
  1. 1. The number of protons in the nucleus of an atom
  2. 4. Positive charge in an atom's nucleus