Ionisation energy and electron affinity of fluorine are respectively `17.42` and `3.45 eV`. Calculate electronegativity of fluorine atom.

Explanation

To calculate the electronegativity of a fluorine atom using the given ionization energy and electron affinity, we can follow these steps:

### Step 1: Identify the given values
- Ionization Energy (IE) of fluorine = 17.42 eV
- Electron Affinity (EA) of fluorine = 3.45 eV

### Step 2: Use Mulliken's electronegativity formula
Mulliken's electronegativity (χ) is calculated using the formula:
\[ \chi = \frac{IE + EA}{2} \]

### Step 3: Substitute the values into the formula
Substituting the given values into the formula:
\[ \chi = \frac{17.42 \, \text{eV} + 3.45 \, \text{eV}}{2} \]

### Step 4: Perform the addition
Calculate the sum of ionization energy and electron affinity:
\[ 17.42 + 3.45 = 20.87 \, \text{eV} \]

### Step 5: Divide by 2
Now, divide the sum by 2 to find the electronegativity:
\[ \chi = \frac{20.87 \, \text{eV}}{2} = 10.435 \, \text{eV} \]

### Step 6: Round the result
Rounding the result gives:
\[ \chi \approx 10.43 \, \text{eV} \]

### Step 7: Calculate Pauling's electronegativity
Using Pauling's scale, the formula is:
\[ \chi_{Pauling} = 0.336 \times \chi_{Mulliken} - 0.2 \]
Substituting the Mulliken electronegativity:
\[ \chi_{Pauling} = 0.336 \times 10.43 - 0.2 \]

### Step 8: Perform the multiplication
Calculate:
\[ 0.336 \times 10.43 = 3.50448 \]

### Step 9: Subtract 0.2
Now, subtract 0.2 from the result:
\[ \chi_{Pauling} = 3.50448 - 0.2 = 3.30448 \]

### Step 10: Round the result
Rounding gives:
\[ \chi_{Pauling} \approx 3.30 \]

### Final Result
The electronegativity of fluorine on Mulliken's scale is approximately **10.43 eV**, and on Pauling's scale, it is approximately **3.30**.

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