Allotropy is due to

Options

A. Differences in the number of atoms in the molecules
B. Difference in the arrangement of atoms in the molecule in the crystal
C. Difference in chemical properties
D. All of these

Answer

### Step-by-Step Solution:

1. **Understanding Allotropy**:
- Allotropy refers to the existence of an element in more than one form in the same physical state. The different forms are called allotropes.

2. **Identifying the Characteristics of Allotropes**:
- Allotropes have the same chemical composition (same type of atoms) but differ in their physical arrangement. This leads to different physical and sometimes chemical properties.

3. **Examples of Allotropes**:
- Common examples include carbon allotropes such as diamond, graphite, and buckminsterfullerene.
- **Diamond**: Has a tetrahedral arrangement of carbon atoms, making it hard and transparent.
- **Graphite**: Has a layered structure with hexagonal rings, allowing layers to slide over each other, making it slippery.
- **Buckminsterfullerene**: Has a spherical structure resembling a soccer ball, composed of 20 hexagonal and 12 pentagonal rings.

4. **Analyzing the Options**:
- The options given are:
- A) Differences in number of atoms in the molecule
- B) Differences in the arrangement of the atoms in the molecule in crystal
- C) Differences in chemical properties
- D) All of these
- Since allotropy is primarily due to differences in the arrangement of atoms in the crystal structure, option B is the most accurate.

5. **Conclusion**:
- The correct answer is B) Differences in the arrangement of the atoms in the molecule in crystal.