The first ionisation potential of Na ,Mg and Si are respectively 496,737 and 786 `Kjmol^-1` the ionisation potential of Al will be closer to

Options

A. `760kjmol^-1`
B. `575kjmol^-1`
C. `801kjmol^-1`
D. `419kjmol^-1`

Answer

To determine the first ionization potential of aluminum (Al) based on the given values for sodium (Na), magnesium (Mg), and silicon (Si), we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Ionization Potential**:
- The first ionization potential (or ionization energy) is the energy required to remove the most loosely bound electron from a neutral gaseous atom.

2. **Identifying the Elements and Their Ionization Potentials**:
- We have the following ionization potentials:
- Na: 496 kJ/mol
- Mg: 737 kJ/mol
- Si: 786 kJ/mol

3. **Recognizing the Periodic Trend**:
- Ionization energy generally increases across a period from left to right due to increasing nuclear charge and decreasing atomic radius.
- The elements Na, Mg, Al, and Si are in the same period (3rd period), with Na in Group 1, Mg in Group 2, Al in Group 13, and Si in Group 14.

4. **Analyzing the Position of Aluminum**:
- Aluminum (Al) is positioned between magnesium (Mg) and silicon (Si) in the periodic table.
- As we move from Na to Mg to Al, we expect the ionization potential to increase, but we also need to consider the electronic configuration.

5. **Considering Electronic Configuration**:
- Magnesium has a fully filled 3s² orbital, making it more stable and requiring more energy to remove an electron.
- Aluminum has the configuration 3s² 3p¹, meaning it has one electron in the 3p orbital, which is easier to remove than an electron from a fully filled orbital.

6. **Estimating the Ionization Potential of Aluminum**:
- Since Al is easier to ionize than Mg but harder than Na, we can conclude that its ionization potential will be between those of Na and Mg.
- Therefore, we can estimate that the ionization potential of Al will be greater than 496 kJ/mol (Na) and less than 737 kJ/mol (Mg).

7. **Choosing an Intermediate Value**:
- A reasonable estimate for the ionization potential of Al would be around 575 kJ/mol, which is between the values for Na and Mg.

8. **Conclusion**:
- The ionization potential of aluminum is closer to 575 kJ/mol.

### Final Answer:
The ionization potential of Al will be closer to **575 kJ/mol**.