Q5 of 27 Page 62

Electronic configurations of elements P, Q, R and S are given below. (These are not actual symbols).

P — 2, 2


Q — 2, 8, 2


R — 2, 8, 5


S — 2, 8


To which group and period does the element R belong?

R belongs to group 5 and period 3

For group:


i. To find out the group number, first we need to find out the number of electrons in the outermost shell of R.


ii. In R, five electrons are present in the outermost shell.


iii. Hence, R belongs to group 5.


For period:


i. To find out the period number, first we need to find out the number of shell present in R.


ii. In R (2,8,5), three shells are present.


iii. Hence, R belongs to period 3.


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