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.

Four elements P, Q, R and S belong to the third period of the Modern P

1.	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» SOLUTION :ELECTRONIC configuration of Q: 2,8, 3 Valency of Q: 3 Electronic configuration of R: 2, 8,5 Valency of R: 8-5 = 3 `UNDERSET(2,8,1)(P) + underset(2,8,7)(S) to PS`