What is the two dimensional coordination number of a molecule in (i) square close-packed layer (ii) hexagonal close-packed layer.

Explanation

To determine the two-dimensional coordination number of a molecule in square close-packed and hexagonal close-packed layers, we can follow these steps:

### Step 1: Understanding Square Close Packing
In square close packing, the arrangement of spheres is such that they are aligned both horizontally and vertically. This means that each sphere in one row is directly above or below the spheres in the adjacent rows.

- **Visualization**: Imagine a grid where each sphere occupies a position, and the spheres in adjacent rows are stacked directly above one another.

### Step 2: Counting Neighbors in Square Close Packing
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