Which of the following may ignite sphontaneously in air ?

Options

A. White phosphorous
B. Red phosphorus
C. Black Phosphorus
D. Nitrogen

Explanation

To determine which of the following substances may ignite spontaneously in air, we will analyze the options provided: white phosphorus, red phosphorus, black phosphorus, and nitrogen.

### Step-by-Step Solution:

1. **Understanding the Properties of Phosphorus Allotropes**:
- Phosphorus exists in several allotropes, including white, red, and black phosphorus. Each allotrope has different chemical properties and reactivity.

2. **Analyzing White Phosphorus**:
- White phosphorus (P4) is known for its high reactivity and flammability. It can ignite spontaneously in air at temperatures as low as 30 degrees Celsius (86 degrees Fahrenheit). This property makes it extremely hazardous and requires it to be stored underwater or in inert gases to prevent accidental ignition.

3. **Analyzing Red Phosphorus**:
- Red phosphorus is more stable and less reactive compared to white phosphorus. It does not ignite spontaneously in air and requires a higher temperature to catch fire.

4. **Analyzing Black Phosphorus**:
- Black phosphorus is the least reactive allotrope of phosphorus. It does not ignite spontaneously in air and is relatively stable at room temperature.

5. **Analyzing Nitrogen**:
- Nitrogen is an inert gas under standard conditions and does not support combustion. It does not ignite spontaneously in air.

6. **Conclusion**:
- Among the options given, only white phosphorus is known to ignite spontaneously in air. Therefore, the correct answer is **Option A: White Phosphorus**.

### Final Answer:
The substance that may ignite spontaneously in air is **White Phosphorus**.

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