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:
- Hydrogen (H)
- Helium (He)
- Lithium (Li)
- Beryllium (Be)
- Boron (B)
- Carbon (C)
- Nitrogen (N)
- Oxygen (O)
- Fluorine (F)
- Neon (Ne)
- Sodium (Na)
- Magnesium (Mg)
- Aluminium (Al)
- Silicon (Si)
- Phosphorous (P)
- Sulphur (S)
- Chlorine (Cl)
- Argon (Ar)
- Potassium (K)
- Calcium (Ca)
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