Question

What is the coordination number of a particle in simple cubic close packed structure?

• A. 12
• B. 4
• C. 6
• D. 8

Hint:

Coordination Numbers to memorize:
1D line = 2
2D Square close packing = 4
2D Hexagonal close packing = 6
3D Simple Cubic (SC) = 6
3D Body Centered (BCC) = 8
3D Close Packed (FCC/CCP/HCP) = 12

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
The question asks for the fundamental coordination number of an atom located within a specific crystalline lattice. (Note: The phrasing "simple cubic close packed" is slightly non-standard. The standard textbook terms are "Simple Cubic" (SC) or "Cubic Close-Packed" (CCP/FCC). However, in context with the options provided, it implies the primitive "Simple Cubic" structure).

Step 2: Detailed Explanation:
The coordination number of an atom in a crystal lattice is defined as the total number of its nearest, immediate, touching neighbors.
Let's evaluate the primary cubic lattices:
1. Simple Cubic (SC): Atoms are placed only at the 8 corners of the cube. If you pick any reference atom, it directly touches its 6 immediate neighbors along the x, y, and z axes (front, back, left, right, top, bottom). Thus, its coordination number is exactly 6.
2. Body-Centered Cubic (BCC): An atom sits exactly in the center of the body diagonal and touches the 8 corner atoms. Thus, its coordination number is 8.
3. Face-Centered Cubic Cubic Close-Packed (FCC/CCP): Atoms are packed extremely tightly in layers (ABCABC...). Every atom touches 6 atoms in its own plane, 3 in the plane above, and 3 in the plane below. Thus, its coordination number is 12.
Because 6 is present in the options and aligns directly with the "simple cubic" portion of the phrase, this is the intended answer.

Step 3: Final Answer:
The coordination number is 6, matching option (c).