Electronic configurations of elements P, Q, R and S are given below :P

1.	Electronic configurations of elements P, Q, R and S are given below :P: 2,8,1; Q: 2,5 R: 2, 8,7: S: 2,8,5Which of the following statements are correct?I. Elements Q and S belong to the same period of the periodic table. II. P is an alkali metal. III. R is a metal.lV. Valency of element S is 3. (A) I and II only (B) II and IV only (C) I and III only (D) All of these
Answer» Correct option (B) II and IV only Explanation: P (2, 8, 1) : group 1, alkali metal Q (2,5): period 2, Group 15, valency 3 R (2,8,7): period 3, group 17, valency 1 , non-metal S (2, 8, 5) period 3, group 15, valency 3, non-metal

Electronic configurations of elements P, Q, R and S are given below :P: 2,8,1; Q: 2,5 R: 2, 8,7: S: 2,8,5Which of the following statements are correct?I. Elements Q and S belong to the same period of the periodic table. II. P is an alkali metal. III. R is a metal.lV. Valency of element S is 3. (A) I and II only (B) II and IV only (C) I and III only (D) All of these

Answer»

Correct option (B) II and IV only

Explanation:

P (2, 8, 1) : group 1, alkali metal

Q (2,5): period 2, Group 15, valency 3

R (2,8,7): period 3, group 17, valency 1 , non-metal

S (2, 8, 5) period 3, group 15, valency 3, non-metal