Question

Atoms of two elements $P$ and $Q$ have $5$ electrons in $2^{nd}$ shell and $3^{rd}$ shell respectively. What could be the geometric representations of $P$ and $Q$? What will be the atomic numbers of these elements?

Answer 1

Electronic configuration of an element is $2^n$ where n is the number of orbit hence

1st orbit can not have more than 2 electrons $2^1=2$

2nd orbit can not have more than 8 electrons $2^2=8$

Electronic configuration of an elements can be $P=2,5=7$ and $Q=2,8,5=15$