The second ionisation potentials in electron volts of oxygen and fluorine atoms are respectively given by

Options

A. `35.1, 38.3`
B. `38.3, 38.3`
C. `38.3, 35.1`
D. `35.1, 35.1`

Explanation

To find the second ionization potentials of oxygen and fluorine, we will follow these steps:

### Step 1: Write the electronic configuration of oxygen.
- Oxygen (O) has an atomic number of 8. Its electronic configuration is:
\[ 1s^2 2s^2 2p^4 \]

### Step 2: Determine the electronic configuration after the first ionization.
- When one electron is removed from oxygen, it becomes O⁺. The electronic configuration of O⁺ is:
\[ 1s^2 2s^2 2p^3 \]

### Step 3: Determine the electronic configuration after the second ionization.
- When a second electron is removed from O⁺, it becomes O²⁺. The electronic configuration of O²⁺ is:
\[ 1s^2 2s^2 2p^2 \]

### Step 4: Write the electronic configuration of fluorine.
- Fluorine (F) has an atomic number of 9. Its electronic configuration is:
\[ 1s^2 2s^2 2p^5 \]

### Step 5: Determine the electronic configuration after the first ionization.
- When one electron is removed from fluorine, it becomes F⁺. The electronic configuration of F⁺ is:
\[ 1s^2 2s^2 2p^4 \]

### Step 6: Determine the electronic configuration after the second ionization.
- When a second electron is removed from F⁺, it becomes F²⁺. The electronic configuration of F²⁺ is:
\[ 1s^2 2s^2 2p^3 \]

### Step 7: Compare the stability of O²⁺ and F²⁺.
- The O²⁺ ion has a half-filled p subshell (2p³), which is more stable due to exchange energy. In contrast, F²⁺ does not have a half-filled subshell.

### Step 8: Conclude the second ionization energies.
- Since O²⁺ is more stable than F²⁺, it requires more energy to remove an electron from O²⁺ than from F²⁺. Thus, the second ionization potential of oxygen is higher than that of fluorine.

### Final Answer:
- The second ionization potentials in electron volts of oxygen and fluorine are such that the second ionization potential of oxygen is greater than that of fluorine.