Question

Iron is a hard metal whereas sodium is a soft metal. Identify the reason.

• A. Low ionization potential value of sodium
• B. High ionization potential value of sodium
• C. More number of free electrons in sodium
• D. More number of free electrons in iron

Answer 1

The correct option is A

Low ionization potential value of sodium

Explanation of correct option:

(A) Low ionization potential value of sodium

• Sodium ($\mathrm{Na}$) has a low ionization potential value because of its large size.
• So, weak metallic bonding exists and sodium is soft in nature.
• Iron ($\mathrm{Fe}$) is strong and tough because it has stronger metallic bonding than sodium.

Explanation of incorrect options:

(B)High ionization potential value of sodium

The electronic configuration of sodium is $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^1$. If it loses the valence electron then it will attain a configuration of the noble gas i.e., $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^6$. Thus, losing this electron is a very facile process and requires very low energy. So, sodium has a low ionization potential value

(C) Sodium has only a single valence that can be released in order to attain a noble gas configuration. So, each sodium release only one electron. So, there are free electrons present in sodium metal but this has no relation to its softness.

(D) Number of free electrons cannot be the reason for the toughness of iron.

Hence, the correct option is (A).