Question

Question 3.10 How does atomic radius vary in a period and in a group? How do you explain the variation?

Class XI Classification of Elements and Periodicity in Properties Page 93

Answer 1

atomic radius decreases as we move from left to right in a period due to a period the electrons enter in the same valance shell and the effective nuclear charge increases with increase atomic number . As a result , the attraction of the nucleus for outer electrons increases and hence, the atomic size decreases . { see the attachment it is clear that atomic size decreases when we move from left to right }

In group when we move from top to bottom , atomic size increases . Actually as we move down the group , number of shells increases by one and the valance shell electrons are farther and farther away from the nucleus. due to this reason, attraction of the nucleus for outer electrons decreases and hence, the size increases { see attachment , this is clear that atomic size increases when we move top to bottom }

Answer 2

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In general, the atomic radius decreases as we move from left to right in a period with an increase in nuclear charge of the element. The atomic radius increases when we go down a group because of the addition of extra shell.