The electronic configuration for some neutral atoms are given below :
(i) `1s^(2),2s^(2),2p^(6),3s^(2)` (ii) `1s^(2),2s^(2)2p^(6),3s^(1)`
(iii) `1s^(2),2s^(2)2p^(6),3s^(2)3p^(2)` (iv) `1s^(2),2s^(2)2p^(6),3s^(2)3p^(3)`
Which of these is expected to have the highest second ionization enthalpy ?

Options

A. Is an alkali metal
B. is a noble metal
C. (i) and (ii)form ionic compounds
D. (iv)has high ionisation enthalpy.

Answer

To determine which of the given electronic configurations has the highest second ionization enthalpy, we need to analyze the configurations step by step.

### Step 1: Identify the elements based on their electronic configurations.

1. **Configuration (i)**: `1s^2 2s^2 2p^6 3s^2`
- This configuration corresponds to Neon (Ne) with atomic number 10, which is a noble gas.

2. **Configuration (ii)**: `1s^2 2s^2 2p^6 3s^1`
- This configuration corresponds to Sodium (Na) with atomic number 11.

3. **Configuration (iii)**: `1s^2 2s^2 2p^6 3s^2 3p^2`
- This configuration corresponds to Silicon (Si) with atomic number 14.

4. **Configuration (iv)**: `1s^2 2s^2 2p^6 3s^2 3p^3`
- This configuration corresponds to Phosphorus (P) with atomic number 15.

### Step 2: Understand the concept of ionization enthalpy.

- **First Ionization Enthalpy**: Energy required to remove the outermost electron from a neutral atom.
- **Second Ionization Enthalpy**: Energy required to remove a second electron after the first has been removed.

### Step 3: Analyze the stability of the resulting ions after the first ionization.

1. **For Ne (i)**: After removing one electron, Ne becomes Ne⁺, which is still stable as it remains a noble gas configuration.

2. **For Na (ii)**: After removing one electron, Na becomes Na⁺, which has the configuration `1s^2 2s^2 2p^6`, a stable noble gas configuration. This means the second ionization will require more energy.

3. **For Si (iii)**: After removing one electron, Si becomes Si⁺, which has the configuration `1s^2 2s^2 2p^6 3s^2 3p^1`. The second ionization will remove an electron from a more stable configuration.

4. **For P (iv)**: After removing one electron, P becomes P⁺, which has the configuration `1s^2 2s^2 2p^6 3s^2 3p^2`. The second ionization will also remove an electron from a relatively stable configuration.

### Step 4: Compare the second ionization enthalpies.

- The second ionization enthalpy is generally higher for elements that achieve a noble gas configuration after the first ionization.
- In this case, Na (from configuration ii) achieves a noble gas configuration after the first ionization, making its second ionization enthalpy significantly higher than the others.

### Conclusion:

The element with configuration (ii) `1s^2 2s^2 2p^6 3s^1` (Sodium) is expected to have the highest second ionization enthalpy because after the first ionization, it achieves a noble gas configuration, which is very stable.