IMAT 2014 Q48 [Electron Configuration]

The atomic numbers of five atoms are given below.

Which atom would have an electronic configuration ending in a p^5?

A. 7
B. 9
C. 5
D. 8
E. 6

Let us write a complete electronic confirguration for this atom. If it’s configuration stops at p^5, it should look like so:


Since it is a neutral atom, we can count the number of electrons present and that number would also be our proton/atomic number.

2+2+5= 9 electrons/protons

Our answer is therefore, B.