A crystalline solid of a pure substance has a face-centred cubic structure with a cell edge of 400 pm. If the density of the substance in the crystal is `8 g cm^(-3)`, then the number of atoms present in 256g of the crystal is `N xx 10^(24)`. The value of `N` is

Explanation

To solve the problem step by step, we will follow these calculations:

### Step 1: Understand the Structure
The crystalline solid has a face-centered cubic (FCC) structure. In an FCC unit cell, there are:
- 8 corner atoms, each contributing \( \frac{1}{8} \) of an atom to the unit cell.
- 6 face-centered atoms, each contributing \( \frac{1}{2} \) of an atom to the unit cell.

### Step 2: Calculate the Number of Atoms in the Unit Cell (Z)
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