MATTER

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Across
  1. 3. a substance that cannot be broken down into simpler substance by physical or chemical means
  2. 5. a particle with about the same mass as a proton but with no electrical charge
  3. 6. anything that has volume and mass
  4. 8. the number of protons in an atom's nucleus
  5. 9. atoms of the same element with different mass numbers
  6. 10. an atom that gains or loses an electron with a net electric charge
Down
  1. 1. the combined number of protons and neurons in an atom
  2. 2. a particle that has mass and a positive electrical charge
  3. 4. a particle with little mass and a negative electric charge
  4. 7. the center of an atom, made up of protons and neutrons