Periodic Table Crossword Puzzle

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Across
  1. 1. Atom with an electrical charge
  2. 5. The number that results from adding protons and neutrons
  3. 7. Particles with no electrical charge
  4. 8. Positive particles in the nucleus of an atom
Down
  1. 2. Electrical charge of an electron
  2. 3. The smallest piece of matter we can have
  3. 4. Particles that move around the nucleus
  4. 6. The charge of a proton