first 20 elements atomic numbers

Here are the atomic numbers for the first 20 elements:

1. Hydrogen (H) - 1

2. Helium (He) - 2

3. Lithium (Li) - 3

4. Beryllium (Be) - 4

5. Boron (B) - 5

6. Carbon (C) - 6

7. Nitrogen (N) - 7

8. Oxygen (O) - 8

9. Fluorine (F) - 9

10. Neon (Ne) - 10

11. Sodium (Na) - 11

12. Magnesium (Mg) - 12

13. Aluminum (Al) - 13

14. Silicon (Si) - 14

15. Phosphorus (P) - 15

16. Sulfur (S) - 16

17. Chlorine (Cl) - 17

18. Argon (Ar) - 18

19. Potassium (K) - 19

20. Calcium (Ca) - 20