Question

Which of the following has the highest 3rd ionization energy?

• A. Mn
• B. V
• C. Cr
• D. Fe

Answer 1

The Correct Option is A

The question asks which element has the highest 3rd ionization energy among Manganese (Mn), Vanadium (V), Chromium (Cr), and Iron (Fe). To determine this, we need to understand the concept of ionization energy and its relation to electronic configuration.

Ionization energy is the energy required to remove an electron from a gaseous atom or ion. The third ionization energy refers to the energy required to remove the third electron from an ion.

For transition metals like Mn, V, Cr, and Fe, it is crucial to consider their electronic configurations:

• Manganese (Mn): [Ar] 3d⁵ 4s²
• Vanadium (V): [Ar] 3d³ 4s²
• Chromium (Cr): [Ar] 3d⁵ 4s¹ (Note: Cr has a configuration that provides extra stability due to a half-filled d-subshell)
• Iron (Fe): [Ar] 3d⁶ 4s²

For the third ionization energy, we look at the stable configurations or the changes in subshell occupation. Mn has a stable half-filled d⁵ configuration after losing its 4s electrons, making it particularly stable. Removing a third electron, which will involve a 3d electron, requires more energy due to this stability.

Therefore, Mn has the highest third ionization energy compared to V, Cr, and Fe due to the stability of its half-filled d⁵ orbital after losing two electrons (first and second ionization) from the 4s orbital.

In conclusion, the correct answer is Mn, as it has the highest 3rd ionization energy due to the significant leap in stability provided by its half-filled d-sub-shell.