Question

265. Ionization enthalpy depends upon

• A. effective nuclear charge
• B. electronegativity
• C. atomic size
• D. electron affinity

Answer 1

Answer: (A), (C)

atomic size

Ionization enthalpy: It is the measure of the force of attraction between the nucleus and the valence electrons. In other words, it is the amount of energy required to remove an electron from an isolated atom or molecule.

Explanation of correct options:

(A) effective nuclear charge:

• Ionization enthalpy α nuclear charge
• As nuclear charge increases among atoms having the same number of energy shells, the Ionization enthalpy increases because of the force of attraction towards the nucleus, and the valence electrons increase.
• Hence, more energy is required to remove the valence electrons.

(C) atomic size:

• Ionization enthalpy α $\frac{1}{\mathrm{SIze}\mathrm{of}\mathrm{atom}}$
• As the distance between the valence electron and the nucleus increases, i.e., as the size of the atom increases, the valence electrons are less tightly held by the nucleus.
• Thus, it becomes easier to remove the valence electrons. Thus ionization enthalpy decreases with increases in atomic size.

Explanation of incorrect option:

(B) electronegativity:

• It is the tendency of an atom to attract the shared electron pair towards itself. Ionization enthalpy does not depend upon electronegativity.

(D) electron affinity:

• The electron affinity of an atom or molecule is defined as the amount of energy released when an electron is added to an isolated gaseous atom. Ionization enthalpy does not depend upon electron affinity because both are different.

Hence, option (A) and (C) is correct.