Question 2 - MCQs from (Past Year Papers & NCERT Exemplar) - Chapter 5 Class 10 - Periodic Classification of Elements

Elements P, Q, R and S have atomic numbers 11, 15, 17 and 18 respectively. Which of them are reactive non-metals?

(a) P and Q

(b) P and R

(c) Q and R

(d) R and S

Answer

The electronic configurations of P, Q, R and S are as follows:

P(11): 2, 8, 1

Q(15): 2, 8, 5

R(17): 2, 8, 7

S(18): 2, 8, 8

Metals lose electrons to attain stability whereas non-metals gain electrons for the same.

Now, checking the options:

• Element P donates 1 electron to attain stability. Hence, it is a metal.
• Element Q accepts 3 electrons to attain stability. Hence it is a non-metal.
• Element R accepts 2 electrons to attain stability. Hence it is a non-metal.
• Element S cannot accept anymore electrons. Hence, it is a noble-gas.

Since Q and R have a high tendency to accept electrons in order to attain noble gas configuration, they are reactive non-metals.

Therefore, the correct option is (c) Q and R