Prove that valency is a periodic property.

1.	Prove that valency is a periodic property.
Answer» SOLUTION :Variation in period: The number of valence electrons INCREASES from 1 to 8 on moving across a period. The valency of the elements with respect to hydrogen and CHLORINE increases from 1 to 4 and then decreases from 4 to zero. Variation in group: On moving down a group, the number of valence electrons remains same. All the elements in a group exhibit same valency. For example, all the elements of group 1 have valency equal to 1. Hence, valency is a periodic property.

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