Question

Four elements P, Q, R and S belong to the third period of the Modern Periodic Table and have respectively 1,3, 5 and 7 electrons in their outermost shells. Write the electronic configurations of Q and R and determine their valencies. Write the molecular formula of the compound formed when P and S combine.

Answer 1

Electronic configuration of Q : 2, 8, 3
Valency of Q: 3
Electronic configuration of R: 2, 8, 5
Valency of R: 8-5=3
P      +      S ----> PS
2,8,1     2,8,7