How many neutrons are present in B and D?

CBSE Class 9 CBSE Class 9 Science
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1

In the following table, the mass number and the atomic number of certain elements are given.

(i) How many neutrons are present in B and D?
(ii) What would be the valency of element ‘B’ listed in the above table?

2

(i) Number of neutrons in B=7 -3 = 4
Number of neutrons in D= 40 -18 = 22
(ii) Electronic configuration of the element B is 2, 1. Therefore, its valency is 1.