Question

How many electrons are present in the valence shells of the central atoms in the molecules of $BeC{l}_2,B{F}_3,PC{l}_5?$

Answer 1

In $BeC{l}_2$

Electronic configuration of $Be:{1s}^2{2s}^2$

Hence no. of valence shell electrons $=2$

In ${BF}_3$

Electronic configuration of $B:{1s}^2{2s}^2{2p}^1$

Hence no. of valence electrons $=3$

In ${PCl}_5$

Electronics configuration of ${PCl}_5$ is ${1s}^2{2s}^2{2p}^6{3s}^2{3p}^3$

Hence, no. of valence electrons $=5$