Correct order of first ionization energy of the following metals Na, Mg, Al, Si in `kJ mol^(–1)` respectively are:

Options

A. 497, 737, 577, 786
B. 497, 577, 737, 786
C. 786, 739, 577, 497
D. 739, 577, 786, 487

Explanation

To determine the correct order of first ionization energy of the metals Na, Mg, Al, and Si, we can follow these steps:

### Step 1: Write the Electron Configurations
- Sodium (Na): The electron configuration is \( [Ne] 3s^1 \).
- Magnesium (Mg): The electron configuration is \( [Ne] 3s^2 \).
- Aluminum (Al): The electron configuration is \( [Ne] 3s^2 3p^1 \).
- Silicon (Si): The electron configuration is \( [Ne] 3s^2 3p^2 \).

### Step 2: Analyze the Number of Valence Electrons
- Na has 1 valence electron.
- Mg has 2 valence electrons.
- Al has 3 valence electrons.
- Si has 4 valence electrons.

### Step 3: Consider the Stability of Electron Configurations
- Magnesium has a completely filled 3s subshell, which is more stable compared to the others.
- The filled subshell in Mg means that removing an electron will require more energy due to the stability of the filled configuration.

### Step 4: Understand the Trend in Ionization Energy
- Ionization energy generally increases across a period due to increasing nuclear charge and decreasing atomic size.
- As we move from Na to Si, the nuclear charge increases, which means that the electrons are held more tightly by the nucleus.

### Step 5: Compare the Ionization Energies
- Based on the above analysis:
- Na has the lowest ionization energy because it has only one electron in the outermost shell and is less tightly bound.
- Al has a higher ionization energy than Na but lower than Mg and Si due to its additional electron in the p-orbital.
- Mg has a higher ionization energy than Na and Al because of its stable filled 3s subshell.
- Si has the highest ionization energy because it is further to the right in the periodic table, with a higher nuclear charge and more tightly bound electrons.

### Step 6: Final Order of Ionization Energies
Based on the analysis, the order of first ionization energy for Na, Mg, Al, and Si is:
- Na < Al < Mg < Si

### Step 7: Convert to kJ mol^(-1)
The approximate values of first ionization energies are:
- Na: 497 kJ/mol
- Al: 577 kJ/mol
- Mg: 737 kJ/mol
- Si: 786 kJ/mol

Thus, the correct order of first ionization energy in kJ/mol is:
- **Na (497) < Al (577) < Mg (737) < Si (786)**