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 Oxides and Their Elements
- \( a = NO_2 \) (Nitrogen Dioxide)
- \( b = K_2O \) (Potassium Oxide)
- \( c = ZnO \) (Zinc Oxide)

### Step 2: Understand Basic Nature of Oxides
The basic nature of oxides is influenced by the electronegativity of the elements. Basic oxides tend to be electron donors, while acidic oxides tend to be electron acceptors. As electronegativity increases, the basic character of the oxide decreases.

### Step 3: Determine Electronegativity of the Elements
- **Nitrogen (N)**: Has a relatively high electronegativity.
- **Potassium (K)**: Has a low electronegativity (being an alkali metal).
- **Zinc (Zn)**: Has moderate electronegativity (higher than potassium but lower than nitrogen).

### Step 4: Rank the Electronegativity
- **Most Electronegative**: Nitrogen (from \( NO_2 \))
- **Moderately Electronegative**: Zinc (from \( ZnO \))
- **Least Electronegative**: Potassium (from \( K_2O \))

### Step 5: Relate Electronegativity to Basic Nature
Since basic character is inversely proportional to electronegativity:
- \( K_2O \) (Potassium Oxide) will have the highest basic character because potassium is the least electronegative.
- \( ZnO \) (Zinc Oxide) will have a moderate basic character.
- \( NO_2 \) (Nitrogen Dioxide) will have the lowest basic character because nitrogen is the most electronegative.

### Step 6: Write the Order of Basic Nature
Thus, the order of basic nature from highest to lowest is:
\[ K_2O > ZnO > NO_2 \]

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