Arrange the elements N, P, O and S in the order of
i) increasing first ionisation enthalpy.
ii) increasing non-metallic character.
Give reason for the arrangement assigned.

Explanation

To solve the question of arranging the elements N (Nitrogen), P (Phosphorus), O (Oxygen), and S (Sulfur) in the order of increasing first ionization enthalpy and increasing non-metallic character, we will follow these steps:

### Step 1: Understanding Ionization Enthalpy
**Definition**: Ionization enthalpy is the amount of energy required to remove an electron from an atom in its gaseous state.

### Step 2: Analyze the Elements
- **Nitrogen (N)**: Atomic number 7, electronic configuration: 1s² 2s² 2p³
- **Oxygen (O)**: Atomic number 8, electronic configuration: 1s² 2s² 2p⁴
- **Phosphorus (P)**: Atomic number 15, electronic configuration: 1s² 2s² 2p⁶ 3s² 3p³
- **Sulfur (S)**: Atomic number 16, electronic configuration: 1s² 2s² 2p⁶ 3s² 3p⁴

### Step 3: Arrange by Increasing First Ionization Enthalpy
- **Trend**: Ionization enthalpy generally increases across a period (left to right) and decreases down a group (top to bottom).
- **Comparing N and O**: Nitrogen has a half-filled p subshell (2p³), which is more stable than Oxygen's (2p⁴). Thus, Nitrogen has a higher ionization enthalpy than Oxygen.
- **Comparing P and S**: Similarly, Phosphorus (3p³) has a half-filled subshell, making it more stable than Sulfur (3p⁴). Therefore, Phosphorus has a higher ionization enthalpy than Sulfur.
- **Final Order**: The order of increasing first ionization enthalpy is:
- Sulfur (S) < Phosphorus (P) < Oxygen (O) < Nitrogen (N)

### Step 4: Arrange by Increasing Non-Metallic Character
**Definition**: Non-metallic character refers to the tendency of an element to gain electrons and form negative ions.

- **Trend**: Non-metallic character increases across a period (left to right) and decreases down a group (top to bottom).
- **Comparing N and O**: Oxygen is more non-metallic than Nitrogen because it is further right in the same period.
- **Comparing P and S**: Sulfur is more non-metallic than Phosphorus for the same reason.
- **Final Order**: The order of increasing non-metallic character is:
- Phosphorus (P) < Sulfur (S) < Nitrogen (N) < Oxygen (O)

### Final Answers
1. **Increasing First Ionization Enthalpy**: S < P < O < N
2. **Increasing Non-Metallic Character**: P < S < N < O