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2015-12-08T19:41:07+05:30

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The first 20 elements of periodic table, their valencies and atomic masses are provided below;
 
1. Hydrogen has valency 1, and atomic mass 1,
2. Helium is inert means its valency is 0, and its atomic mass is 4
3. Lithium has valency 1,  and atomic mass 6.94
4. Beryllium has valency 2, and atomic mass 9
5. Boron has valency 3, and atomic mass 10.81
6. Carbon has valencies 2 and 4, and atomic mass 12
7. Nitrogen has valencies 3 and 5, and atomic mass 14
8. Oxygen has valency 2, and atomic mass 16
9. Fluorine has valency 1, and atomic mass 19
10. Neon is neutral means  its valency is 0, and its mass is 20
11.Sodium has valency 1, and atomic mass 22.99
12.Magnesium has valency 2, and atomic mass 24.31
13.Aluminum has valency 3, and atomic mass 27
14. Silicon has valency 4, and atomic mass 28
15. Phosphorous has valencies 3 and 5, and atomic mass 31
16. Sulfur has valencies 2,4, and 6, and atomic mass 32
17. Chlorine has valencies, 1,3,5,7, and atomic mass 35.45
18. Argon is neutral means its valency is 0, and its mass is 40
19. Potassium has valency 1, and atomic mass 39
20. Calcium has valency 2, and atomic mass 40

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