Question

Question 10. Which of these belong to the same period?
Element
A
B
c.
2
10 5
Atomic
number
(a) A, B
(b) B, C
(c) C, A
(d) A, B and C​

Answer 1

Answer:

(a)

Explanation:

Atomic no. of A is 2

B is 10

and C is 5

Noble gas are those elements which have their shells completely filled. Eg- (2), (2, 8), (2, 8,18)

Electronic configuration of A is

=> 2 (noble gas)

B is

=> 2,8 (noble gas)

C is

=> 2,3 (incomplete so, not a noble gas)

So A and B are in same period as all noble gases are kept in same period.

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