Two `p`-block elements `x` (outer configuration `ns^(2) np^(3)`) and `z` (outer configuration `ns^(2) np^(4)`) occupy neighbouring positions in a period. Using this information which of the following is correct with respect to their ionisation potential `I_(x)` and `I_(z)`.

Options

A. `I_(x) gt I_(z)`
B. `I_(z) gt I_(x)`
C. `I_(z) = I_(x)`
D. Relation between `I_(x)` and `I_(x)` is uncertain

Explanation

To solve the problem regarding the ionization potentials of the two p-block elements \( x \) and \( z \), we will follow these steps:

### Step 1: Identify the outer electronic configurations
- Element \( x \) has the outer electronic configuration \( ns^2 np^3 \).
- Element \( z \) has the outer electronic configuration \( ns^2 np^4 \).

### Step 2: Determine the stability of the configurations
- The configuration \( np^3 \) (for element \( x \)) is a half-filled configuration. Half-filled subshells are generally more stable due to symmetry and exchange energy.
- The configuration \( np^4 \) (for element \( z \)) is not half-filled and is less stable compared to half-filled configurations.

### Step 3: Analyze the ionization potential
- Ionization potential (or ionization energy) is the energy required to remove an electron from an atom in the gaseous state.
- Since element \( x \) has a more stable half-filled configuration, it will require more energy to remove an electron compared to element \( z \), which has a less stable configuration.

### Step 4: Compare the ionization potentials
- Therefore, we can conclude that:
\[ I_x > I_z \]
This means that the ionization potential of element \( x \) is greater than that of element \( z \).

### Final Conclusion
The correct relationship between the ionization potentials is:
\[ I_x > I_z \]