If a = `NO_2, b = K_2 O, c = ZnO`. These oxides in the decreasing order of basic nature will be:

Options

A. `a gt b gt c`
B. `b gt c gt a`
C. `c gt b gt a`
D. `a gt c gt b`

Answer

To determine the decreasing order of basic nature of the oxides \( NO_2 \), \( K_2O \), and \( ZnO \), we can follow these steps:

### Step 1: Identify the Nature of Each Oxide
- **\( NO_2 \)**: This is a non-metal oxide. Non-metal oxides are generally acidic in nature.
- **\( K_2O \)**: This is a metal oxide (specifically, an alkali metal oxide). Metal oxides are typically basic.
- **\( ZnO \)**: This is also a metal oxide, but zinc is a transition metal and its oxides can exhibit amphoteric behavior (can act as both acid and base).

### Step 2: Compare Basic Nature
- **Basicity of \( K_2O \)**: As an alkali metal oxide, \( K_2O \) is strongly basic.
- **Basicity of \( ZnO \)**: While \( ZnO \) is also a metal oxide, it is less basic than alkali metal oxides due to its amphoteric nature. It can react with both acids and bases but does not exhibit strong basic properties.
- **Basicity of \( NO_2 \)**: Being a non-metal oxide, it is acidic and thus has the least basic nature.

### Step 3: Arrange in Decreasing Order
Based on the analysis:
1. **\( K_2O \)** - Strongly basic
2. **\( ZnO \)** - Moderately basic (amphoteric)
3. **\( NO_2 \)** - Acidic (least basic)

Thus, the decreasing order of basic nature is:
\[ K_2O > ZnO > NO_2 \]

### Final Answer
The correct order of the oxides in decreasing order of basic nature is:
\[ K_2O > ZnO > NO_2 \]