What is the coordination number in a square close packed structure in two dimensions ?

Options

A. 2
B. 3
C. 4
D. 6

Explanation

To determine the coordination number in a square close packed structure in two dimensions, we can follow these steps:

### Step 1: Understand the Structure
In a square close packed structure, the spheres (or atoms) are arranged in a two-dimensional grid. Each sphere is positioned directly above and below other spheres in the same column, and directly next to other spheres in the same row.

**Hint:** Visualize the arrangement as a grid where each sphere occupies a corner of a square.

### Step 2: Identify the Neighbors
In this arrangement, each sphere is in contact with other spheres. Specifically, a sphere in the center of this arrangement will be in contact with four neighboring spheres: one directly above, one directly below, one to the left, and one to the right.

**Hint:** Count the spheres that are directly adjacent to any given sphere.

### Step 3: Calculate the Coordination Number
The coordination number is defined as the number of nearest neighbors surrounding a central atom (or sphere). In the square close packed structure, since each sphere is in contact with four other spheres, the coordination number is 4.

**Hint:** Remember that the coordination number reflects how many immediate neighbors each sphere has.

### Conclusion
The coordination number in a square close packed structure in two dimensions is 4.

**Final Answer:** Coordination number = 4

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