JEE Main · 2019 · 12 Apr 2019 · Shift 1 · Classification of Elements and Periodicity

The group number, number of valence electrons and valency of an element with atomic number 15, respectively, are:

Answer: (A)

Solution

Atomic number

15

is phosphorus, with configuration

1 s^{2} 2 s^{2} 2 p^{6} 3 s^{2} 3 p^{3}

. Its outermost shell is the third, so it sits in period

3

, and with five electrons in that shell (

3 s^{2} 3 p^{3}

) it belongs to group

15

and has

5

valence electrons. The three unpaired

3 p

electrons give it a valency of

3

. So the group number, valence electrons and valency are

15, 5

and

3

JEE Main · 2019 · 12 Apr 2019 · Shift 1 · Single correct option