Question

Given below are two statements:
Statement I: The first ionization enthalpy of Cr is lower than that of Mn.
Statement II: The second and third ionization enthalpies of Cr are higher than those of Mn.
In the light of the above statements, choose the correct answer from the options given below:

• A. Both Statement I and Statement II are true
• B. Statement I is true but Statement II is false
• C. Statement I is false but Statement II is true
• D. Both Statement I and Statement II are false

Hint:

Exceptional stability of half-filled and fully-filled subshells strongly influences ionization enthalpies of transition elements.

Answer 1

The Correct Option is A

To determine the correctness of the given statements regarding the ionization enthalpies of chromium (Cr) and manganese (Mn), we need to understand the electronic configurations and properties of these elements.

1. Understanding Ionization Enthalpy:
   • Ionization enthalpy is the energy required to remove an electron from an isolated gaseous atom or ion.
   • The first ionization enthalpy concerns the removal of the first electron, while the second and third involve removing further electrons.
2. Electronic Configurations:
   • Chromium (Cr): [Ar] 3d⁵ 4s¹
   • Manganese (Mn): [Ar] 3d⁵ 4s²

   Cr has a half-filled d-orbital configuration, while Mn has a more stable half-filled d-config with a filled 4s orbital.

3. Analysis of Statement I:
   • First ionization enthalpy of Cr is lower than Mn because Cr can achieve a more stable configuration (half-filled stable state) upon losing one electron.
   • Thus, Statement I is true.
4. Analysis of Statement II:
   • For the second and third ionization enthalpies:
     • Cr already has a half-filled configuration after losing the first electron, increasing the energy required to remove more electrons.
     • Mn, after losing one electron, will have a more stable configuration upon losing additional electrons.
   • Hence, the second and third ionization enthalpies of Cr are higher than those of Mn.
   • Thus, Statement II is true.
5. Conclusion:
   • Based on the above analysis, both statements are true.
   • This concurs with the option: Both Statement I and Statement II are true.