Periodic trends puzzle project

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Across
  1. 4. used in pools
  2. 10. a nutrient for plants, has the smallest atomic radius in 2p because it is a cation
  3. 11. is named after coal
  4. 12. charge -1, has a mass of 19.00
  5. 13. used to blow up balloons
  6. 14. 5 valence electrons, makes up 78% of earth's atmosphere
  7. 17. floats in water, has 3 protons
  8. 18. a stable element
Down
  1. 1. produced by natural waste, 1 smaller energy level that oxygen
  2. 2. metal, used in fireworks/sparklers, 12 protons
  3. 3. makes up 90%of the atoms in the universe, Hydrogen has a smaller atomic radius to Beryllium
  4. 5. average atomic mass of 20.18
  5. 6. has 11 electrons,11 protons, and 12 neutrons
  6. 7. used for insulation on electrical products, [Ne] 3s^2 3p^4
  7. 8. 8 protons
  8. 9. is used for technology, has a mass of 9.012
  9. 15. used to detect gas leaks, smells like rotten eggs
  10. 16. used for cooking, has more protons than Mg