The formula Na₂HPO₄ consists of the following atoms:
- Sodium (Na): 2 atoms
- Hydrogen (H): 1 atom
- Phosphorus (P): 1 atom
- Oxygen (O): 4 atoms
Adding these together:
2 (Na) + 1 (H) + 1 (P) + 4 (O) = 8 atoms total.
Therefore, the correct answer is eight.