Past Year - 3 Mark Questions

Class 10
Chapter 5 Class 10 - Periodic Classification of Elements

## (vi) The formula of their chlorides.

A and B both belong to third period which means they have 3 shells

 Characteristic A B Electronic Configuration 2, 8, 2 2, 8, 3 Valency 2 3 Number of electrons 12 13 Size of atoms Bigger Smaller Tendency to lose electrons More Less Formula of their oxides AO B 2 O 3 Metallic Character More metallic Less Metallic Formula of chlorides ACl 2 BCl 3

Explanation:

1. Number of electrons in

• A = 12
• B = 13

2. The size of A is bigger than that of B because they belong to the same period and across the period size decreases.

3. As the size increases, the tendency to lose electrons increases. So, it is more for A.

4. The valency of A is 2 and the valency of O is also 2 . So, the formula of its oxide will be AO.

The valency of B is 3 and that of O is 2. So, the formula of its oxide will be B 2 O 3 .

5. Metallic character depends on the tendency to lose electrons . So, it will be more for A.

6. A has a valency of 2 and that of chloride is 1 . So the formula of its chloride is ACl 2

B has a valency of 3 and that of chloride is 1 . So, the formula of its chloride is BCl 3

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