Most crystals show good cleavage because their atoms ions or molecules are

Options

A. weakly bonded together
B. strongly bonded together
C. spherically symmetrical
D. arranged in planes

Explanation

To answer the question "Most crystals show good cleavage because their atoms, ions, or molecules are...", we can break down the explanation into a step-by-step solution.

### Step-by-Step Solution:

1. **Understanding Types of Solids**:
- Solids can be classified into two main categories: crystalline solids and amorphous solids. Crystalline solids have a well-defined geometric structure, while amorphous solids lack this order.

2. **Defining Crystalline Solids**:
- Crystalline solids are characterized by their orderly arrangement of atoms, ions, or molecules. This arrangement allows them to be cut cleanly along specific planes.

3. **Cleavage in Crystalline Solids**:
- The term "cleavage" refers to the tendency of a crystal to split along specific planes. This occurs because the atoms, ions, or molecules in crystalline solids are arranged in layers or sheets that are stacked on top of each other.

4. **Example of Cleavage**:
- For instance, when a crystal of sodium chloride (NaCl) is cut, it breaks along the planes where the ionic bonds are weaker, resulting in smooth, flat surfaces. This is due to the regular arrangement of Na+ and Cl- ions in the crystal lattice.

5. **Comparison with Amorphous Solids**:
- In contrast, amorphous solids, such as glass, do not have a regular arrangement of particles. When they are broken, they do not cleave along defined planes, resulting in irregular and jagged surfaces.

6. **Conclusion**:
- Therefore, the reason most crystals show good cleavage is that their atoms, ions, or molecules are arranged in planes, allowing them to break cleanly along these planes.

### Final Answer:
Most crystals show good cleavage because their atoms, ions, or molecules are arranged in planes.

---