Chemistry revision

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Across
  1. 2. Gain of electrons
  2. 3. Which group of atoms gain 3 electrons?
  3. 5. ____ number that tells us the total number of protons and neutrons in an atom
  4. 8. Polyatomic ion with the formula NH3
  5. 9. Which group one element produces a flame when reacting with water?
  6. 10. How many elements exist as diatomic elements?
  7. 11. H2O2 is the _________ formula of hydrogen peroxide
  8. 12. A compound that comprises of non-metal(s) only
Down
  1. 1. Another name for the halogen-halide reaction
  2. 2. The 'r' in RFM
  3. 4. Atoms of the same element with the same number of protons but a different number of neutrons
  4. 5. Unit of measurement for the amount of something
  5. 6. A diagram that can be used to explain the formulae of compounds
  6. 7. A positive ion
  7. 10. How many protons do carbon atoms have?
  8. 13. atoms In the first shell of electrons (in word form)