Question

What are the mass numbers of the 20 elements?

Answer 1

Here are the mass numbers of the first 20 elements in the periodic table:

1. Hydrogen (H) - Mass Number: 1
2. Helium (He) - Mass Number: 4
3. Lithium (Li) - Mass Number: 7
4. Beryllium (Be) - Mass Number: 9
5. Boron (B) - Mass Number: 11
6. Carbon (C) - Mass Number: 12
7. Nitrogen (N) - Mass Number: 14
8. Oxygen (O) - Mass Number: 16
9. Fluorine (F) - Mass Number: 19
10. Neon (Ne) - Mass Number: 20
11. Sodium (Na) - Mass Number: 23
12. Magnesium (Mg) - Mass Number: 24
13. Aluminum (Al) - Mass Number: 27
14. Silicon (Si) - Mass Number: 28
15. Phosphorus (P) - Mass Number: 31
16. Sulfur (S) - Mass Number: 32
17. Chlorine (Cl) - Mass Number: 35.5 (approximately)
18. Argon (Ar) - Mass Number: 40
19. Potassium (K) - Mass Number: 39
20. Calcium (Ca) - Mass Number: 40

Please note that the mass numbers mentioned above are approximate, as elements may have different isotopes with slightly different mass numbers. The values provided are the most common or stable isotopes for each element.