* Sodium Iodide (NaI): The melting point of sodium iodide is approximately 661 °C (1222 °F).

* Naphthalene (C₁₀H₈): The melting point of naphthalene is approximately 80 °C (176 °F).

Calculating the Difference:

661 °C (NaI) - 80 °C (Naphthalene) = 581 °C

Therefore, the difference in melting point between sodium iodide and naphthalene is approximately 581 °C.