Question

What is the minimum number of forms that an actual crystal must containin Class 1 (Pedial) of the Triclinic System?

• A. 1
• B. 2
• C. 3
• D. 4

Answer 1

The Correct Option is D

The question asks about the minimum number of forms a crystal must contain in Class 1 (Pedial) of the Triclinic System. To answer this, we must understand the basics of crystallography, especially the forms within the triclinic crystal system.

1. **Crystallography Basics:** - A crystal form is a group of crystal faces, all of which have the same relation to the elements of symmetry. - In the triclinic system, there is no axis of symmetry, no plane of symmetry, and no center of symmetry. It is one of the most asymmetrical systems.

2. **Pedial Class of Triclinic System:** - The Pedial class (Class 1) in the triclinic system is the simplest form because it lacks symmetry elements beyond identity. - Due to the lack of symmetry, all faces are independent, implying that none of them can be inter-related by symmetry. Thus, they must be counted individually.

3. **Determining the Minimum Number of Forms:** - The minimum number of independent forms for any crystal in the pedial class, given its asymmetry, would naturally account for the independent faces that define the crystal structure. - Each face of the crystal in this system forms its type, indicating the minimum number here is not just one free face but the minimal independent set that makes the crystal stable yet basic.

4. **Conclusion:** - The minimum number of forms that a crystal must contain in the Pedial class of the triclinic system is 4, as all forms are fundamentally independent with no symmetry to reduce their count.

Therefore, the correct answer is 4.