Elements and Compounds

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Across
  1. 4. Essential for breathing of animals and human beings.
  2. 5. Made up of more than one type of atom.
  3. 7. Carbon oxide that has only one atom of oxygen.
  4. 9. Gas inside the tubes used for advertising.
  5. 10. Its molecule has 8 atoms.
  6. 11. Lithium, potassium, magnesium, aluminium, and iron are ... .
  7. 13. Yellow-green, poisonous gas.
  8. 14. Made up of one type of atom.
  9. 17. This compound contains atoms of calcium, carbon, and oxygen.
  10. 18. Silvery-white metal that makes up table salt in reaction with chlorine.
  11. 19. Element with the symbol "C".
  12. 20. Element with the atomic number 7.
Down
  1. 1. Hydrogen oxide.
  2. 2. Element with the symbol "P".
  3. 3. The lightest element on the Periodic table.
  4. 6. Boron, carbon, oxygen, neon, and sulfur are ... .
  5. 8. Element with the atomic number 13.
  6. 12. This compound has atoms of nitrogen, potassium, and oxygen.
  7. 15. This compound is made up of magnesium and oxygen.
  8. 16. Greenhouse gas.