The first ionization energy is smallest for the atom with electronic configuration?

Options

A. `ns^2 np^3 `
B. `ns^2 np^4 `
C. `ns^2 np^5 `
D. `ns^2 np^6`

Answer

To determine which electronic configuration corresponds to the smallest first ionization energy, we need to analyze the stability of the configurations and the effective nuclear charge experienced by the outermost electrons. Here’s a step-by-step solution:

### Step 1: Understand Ionization Energy
Ionization energy is the amount of energy required to remove an electron from an atom in its gaseous state. Generally, the more stable the electron configuration, the higher the ionization energy required to remove an electron.

**Hint:** Remember that stable configurations (like fully filled or half-filled subshells) require more energy to remove an electron.

### Step 2: Identify the Electronic Configurations
We need to consider the electronic configurations provided in the question. Common configurations to analyze might include:
- p3
- p4
- p5
- np6

**Hint:** Look for configurations that are either half-filled or fully filled, as these are generally more stable.

### Step 3: Analyze Stability of Configurations
- **p3 Configuration:** This is half-filled (e.g., nitrogen). Half-filled configurations are relatively stable.
- **p4 Configuration:** This has four electrons in the p subshell. It is less stable than p3.
- **p5 Configuration:** This has five electrons in the p subshell. It is more stable than p4 but less stable than p6.
- **np6 Configuration:** This is fully filled (e.g., neon). Fully filled configurations are very stable.

**Hint:** The more stable the configuration, the higher the ionization energy. Less stable configurations will have lower ionization energies.

### Step 4: Compare Ionization Energies
- **p3:** Higher ionization energy due to half-filled stability.
- **p4:** Lower ionization energy compared to p3, as it is less stable.
- **p5:** Higher ionization energy than p4 but lower than p6 due to increased stability.
- **np6:** Highest ionization energy due to full stability.

**Hint:** The trend indicates that as we move from p3 to np6, the ionization energy generally increases.

### Step 5: Conclusion
From the analysis, the configuration with the smallest first ionization energy is **p4**. This is because it is less stable than p3 and np6 and requires the least amount of energy to remove an electron.

**Final Answer:** The first ionization energy is smallest for the atom with electronic configuration **p4**.