A cubic unit cell has one atom on each corner and one atom on each body diagonal. The number of atoms in the unit cell is

Explanation

To determine the number of atoms in the given cubic unit cell, we will analyze the contributions from the atoms located at the corners and those located on the body diagonals.

### Step-by-Step Solution:

1. **Identify the Atoms at the Corners:**
- A cubic unit cell has 8 corners.
- Each corner atom is shared among 8 adjacent unit cells.
- Therefore, the contribution of each corner atom to the unit cell is \( \frac{1}{8} \).

\[ \text{Total contribution from corner atoms} = 8 \times \frac{1}{8} = 1 \text{ atom} \]

2. **Identify the Atoms on the Body Diagonals:**
- A cube has 4 body diagonals.
- Each body diagonal has 1 atom located on it.
- Since these atoms are entirely within the unit cell, their contribution is counted as 1 for each body diagonal.

\[ \text{Total contribution from body diagonal atoms} = 4 \times 1 = 4 \text{ atoms} \]

3. **Calculate the Total Number of Atoms in the Unit Cell:**
- Now, we sum the contributions from the corner atoms and the body diagonal atoms.

\[ \text{Total number of atoms in the unit cell} = 1 \text{ (from corners)} + 4 \text{ (from body diagonals)} = 5 \text{ atoms} \]

### Final Answer:
The total number of atoms in the unit cell is **5**.