Explain vakency with suitable example

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.

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a manufacturer of printed circuit boards uses exponential smoothing with trend to forecast monthly demand of its product. at the end of december, the company wishes to forecast sales for january. the estimate of trend through november has been 200 additional boards sold per month. average sales have been around 1000 units per month. the demand for december was 1100 units. the company uses α = 0.20 and β = 0.10. make a forecast including trend for the month of january.