Answer:
The first 20 elements of the periodic table :
1.H —Hydrogen
2.He—Helium
3.Li—Lithium
4.Be—Beryllium
5.B—Boron
6.C—Carbon
7.N—Nitrogen
8.O—Oxygen
9.F—Fluorine
10.Ne—Neon
11.Na—Sodium
12.Mg—Magnesium
13.Al—Aluminum
14.Si—Silicon
15.P—Phosphorus
16.S—Sulfur
17.Cl—Chlorine
18.Ar—Argon
19.K—Potassium
20.Ca—Calcium
The valency of first 20 elements is as follows :-
1. Hydrogen (H) = 1
2. Helium (He) = 0
3. Lithium (Li) = 1
4. Beryllium (Be) = 2
5. Boron (B) = 3
6. Carbon (C) = 4
7. Nitrogen (N) = 3
8. Oxygen (O) = 2
9. Fluorine (F) =1
10. Neon (Ne) = 0
11. Sodium (Na) = 1
12. Magnesium (Mg) = 2
13. Aluminium (Al) = 3
14. Silicon (Si) = 4
15. Phosphorus (P) = 3, 5
16. Sulphur (S) = 2
17. Chlorine (Cl) = 1
18. Argon (Ar) = 0
19. Potassium (K) = 1
20. Calcium (Ca) = 2
Explanation:
First 20 elements in the periodic table start with H and end with Ca. The quickest way to remember the number of valence electrons is to form a relationship with the number of the group the element is located in.
