# a. 3Li, 14Si, 2He, 11Na, 15P Which of these elements belong to be period 3?

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Write down the electronic configuration of the following elements from the given atomic numbers. Answer the following question with explanation.

a. 3Li, 14Si, 2He, 11Na, 15P Which of these elements belong to be period 3?

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Electronic configuration of the following elements is:
3Li = 2,1
14Si =2,8,4
2He= 2
11Na = 2,8,1
15P = 2,8,5
According to electronic configuration of 14Si, 11Na, 15P, each element contains three shell i.e. K,L,M. , Hence belong to the third period