The first 20 element

hydrogen (H)

1 proton, 1 electron, 0 neutron

Helium (He)

2 protons, 2 electrons, 2 neutrons

Lithium (Li)

3 protons, 3 electrons, 4 neutrons

Beryllium (Be)

4 protons, 4 electrons, 5 neutrons

Boron (B)

5 protons, 5 electrons, 6 neutrons

Carbon (C)

6 protons, 6 electrons, 6 neutrons

Nitrogen (N)

7 protons, 7 electrons, 7 neutrons

Oxygen (O)

8 protons, 8 electrons, 8 neutrons

Fluorine (F)

9 protons, 9 electrons, 10 neutrons

Neon (Ne)

10 protons, 10 electrons, 10 neutrons

Sodium (Na)

11 protons, 11 electrons, 12 neutrons

Magnesium (Mg)

12 protons, 12 electrons, 12 neutrons

Aluminium (Al)

13 protons, 13 electrons, 14 neutrons

Slilcon (Si)

14 protons, 14 electrons, 14 neutrons

Phosphorus (P)

15 protons, 15 electrons, 16 neutrons

Sulphur (S)

16 protons, 16 eletrons, 16 neutrons

Chlorine (Cl)

17 protons, 17 electrons, and 18 neutrons

Argon (Ar)

18 protons, 18 electrons, 22 neutrons

Potassium (K)

19 protons, 19 electrons, 20 neutrons

Calcium (Ca)

20 protons, 20 eletrons, 20 neutrons