First 20 elements

Now that we understand what symbols, atomic numbers and atomic masses are, we are ready to focus on the first 20 elements of the periodic table.
A list of the first 20 elements is shown below:

Element Symbol Atomic Number Atomic Mass Number of Protons Number of Neutrons
Hydrogen H 1 1 1 0
Helium He 2 4 2 2
Lithium Li 3 7 3 4
Beryllium Be 4 9 4 9
Boron B 5 11 5 6
Carbon C 6 12 6 6
Nitrogen N 7 14 7 7
Oxygen O 8 16 8 8
Fluorine F 9 18 9 9
Neon Ne 10 20 10 20
Sodium Na 11 23 11 12
Magnesium Mg 12 24 12 12
Aluminum Al 13 27 13 14
Silicon Si 14 28 14 14
Phosphorous P 15 31 15 16
Sulphur S 16 32 16 16
Chlorine Cl 17 35 17 16
Argon Ar 18 40 18 22
Potassium K 19 39 19 20
Calcium Ca 20 40 20 20

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