What does is mean by the first 20 elements?

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The first 20 elements are the elements listed down in the periodic table from Hydrogen to Calcium. They are numbered according to their Atomic Number. It is a general term that as the Atomic number increases, the Atomic weight increases as well (some exemption on Ar and K). Here is the list of the first 20 elements:


  1. Hydrogen (H)
  2. Helium (He) 
  3. Lithium (Li)
  4. Beryllium (Be)
  5. Boron (B)
  6. Carbon (C)
  7. Nitrogen (N)
  8. Oxygen (O)
  9. Fluorine (F)
  10. Neon (Ne)
  11. Sodium (Na)
  12. Magnesium (Mg)
  13. Aluminium (Al)
  14. Silicon (Si)
  15. Phosphorous (P)
  16. Sulphur (S)
  17. Chlorine (Cl)
  18. Argon (Ar)
  19. Potassium (K)
  20. Calcium (Ca)
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