There are four elements P,Q, R and $ and their atomic numbers are 2. 6, 13 and 18, respectively. Which of the following pairs has elements having similar valency?

Correct option is C

The correct option is (C)  P and S

Information booster:

To determine which pair of elements have similar valency, we need to understand the number of valence electrons for each element, as valency is determined by the number of electrons an atom can gain, lose, or share to achieve a stable electron configuration.

Given atomic numbers:

• P (Atomic number 2): This is Helium (He), which has 2 electrons. It has a full outer shell, so its valency is 0 (inert gas).
• Q (Atomic number 6): This is Carbon (C), which has 4 valence electrons. Carbon usually forms 4 bonds (valency = 4).
• R (Atomic number 13): This is Aluminum (Al), which has 3 valence electrons. Aluminum usually loses 3 electrons, so its valency is 3.
• S (Atomic number 18): This is Argon (Ar), which has 8 valence electrons. Argon has a full outer shell and is chemically inert, so its valency is 0.

Now, let’s compare the valency of the elements:

• Helium (P) and Argon (S) both have a valency of 0 because they are noble gases and have full outer electron shells.
• Carbon (Q) has a valency of 4, and Aluminum (R) has a valency of 3. These values are different, so this pair doesn't have similar valency.

So, the correct answer is P and S.