Question

Ionisation Enthalpy $(\mathrm{\Delta }\mathrm{H})1\mathrm{Kj}{\mathrm{Mol}}^{-1})$ For The Elements Of Group 13 Follows The Order:

• A. (A) $\mathrm{B}>\mathrm{Al}<\mathrm{Ga}>\mathrm{In}<\mathrm{Tl}.$
• B. (B) $\mathrm{B}>\mathrm{Al}>\mathrm{Ga}>\mathrm{In}>\mathrm{Tl}.$
• C. (C) $\mathrm{B}<\mathrm{Al}>\mathrm{Ga}<\mathrm{In}>\mathrm{Tl}.$
• D. (D) $\mathrm{B}<\mathrm{Al}>\mathrm{Ga}>\mathrm{In}>\mathrm{Tl}.$

Answer 1

The correct option is B

(B) $\mathrm{B}>\mathrm{Al}>\mathrm{Ga}>\mathrm{In}>\mathrm{Tl}.$

Explanation for correct answer

Correct answer: (B) $\mathrm{B}>\mathrm{Al}>\mathrm{Ga}>\mathrm{In}>\mathrm{Tl}.$

Ionization energy

• Ionization energy is the minimum amount of energy required to remove the loosely bounded electron from an atom.
• On moving from left to right in the periodic table ionization energy increases as the nuclear charge increases.
• On moving down the group in the periodic table, the force of attraction between electrons and nucleus decreases. Therefore, Ionization energy decreases on moving down the group.
• On moving down the group in the Periodic table from Boron (B) to Thallium (Tl), there is a regular decrease in the ionization energy, due to screening effect.$\mathrm{B}>\mathrm{Al}>\mathrm{Ga}>\mathrm{In}>\mathrm{Tl}.$

Therefore, option (B) is correct.

Explanation for incorrect answer

(A) Since, Ionization energy decreases on moving down the group. Therefore, option (A) $\mathrm{B}>\mathrm{Al}<\mathrm{Ga}>\mathrm{In}<\mathrm{Tl}.$ is incorrect.

(C) Boron has highest ionization enthalpy. therefore, option (B) is incorrect.

(D) Boron has highest ionization enthalpy, than aluminum, therefore, option (D) is incorrect.