Choose the correct pair regarding `IE_(3)`

Options

A. `Mn gt Cr`
B. `Mn gt Fe`
C. `Zn gt Cu`
D. All of these

Answer

To solve the question regarding the third ionization energy (IE₃) and to choose the correct pair, we will analyze the ionization energies of the given elements: manganese (Mn), chromium (Cr), copper (Cu), and zinc (Zn).

### Step-by-Step Solution:

1. **Understanding Ionization Energy (IE):**
- Ionization energy is the energy required to remove an electron from an atom in its gaseous state. The third ionization energy (IE₃) refers to the energy needed to remove the third electron from a cation.

2. **Electron Configurations:**
- Write the electron configurations for the elements:
- Manganese (Mn): [Ar] 3d⁵ 4s²
- Chromium (Cr): [Ar] 3d⁵ 4s¹
- Copper (Cu): [Ar] 3d¹⁰ 4s¹
- Zinc (Zn): [Ar] 3d¹⁰ 4s²

3. **Analyzing Third Ionization Energy:**
- For Mn (after removing two electrons, it becomes Mn²⁺: [Ar] 3d⁵):
- The third ionization energy will involve removing an electron from a half-filled 3d subshell (3d⁵), which is relatively stable. Thus, IE₃ for Mn will be high due to stability.
- For Cr (after removing two electrons, it becomes Cr²⁺: [Ar] 3d⁴):
- The third ionization energy will involve removing an electron from a less stable configuration (3d⁴), hence it will be lower than that of Mn.
- For Cu (after removing two electrons, it becomes Cu²⁺: [Ar] 3d⁹):
- Removing an electron from a 3d⁹ configuration is less stable than a fully filled 3d (Cu) but more stable than Cr²⁺.
- For Zn (after removing two electrons, it becomes Zn²⁺: [Ar] 3d¹⁰):
- The third ionization energy will involve removing an electron from a fully filled 3d subshell (3d¹⁰), which is stable. Thus, it will require a significant amount of energy.

4. **Comparing the Ionization Energies:**
- Based on the stability of the electron configurations after the removal of electrons:
- Mn > Zn > Cu > Cr in terms of IE₃.
- Therefore, the correct pairs regarding IE₃ would be:
- Mn has the highest IE₃ due to its half-filled stability.
- Zn has a high IE₃ due to its fully filled configuration.
- Cu has a moderate IE₃.
- Cr has the lowest IE₃.

5. **Conclusion:**
- The correct pairs regarding the third ionization energy are:
- Mn > Cr (Mn has higher IE₃ than Cr)
- Zn > Cu (Zn has higher IE₃ than Cu)
- Thus, the answer is that all the mentioned pairs correctly reflect the trends in third ionization energy.