Melting points rise across the period 3 metals, from sodium near 98 degrees Celsius through magnesium near 650 to aluminum near 660. What accounts for the increase?

Core Concept

Metallic bond strength grows with the number of valence electrons donated to the shared sea and with the core charge pulling them back. Sodium gives one electron per Na⁺ center, magnesium two per Mg²⁺, and aluminum three per Al³⁺. Greater electrostatic cohesion per atom means more thermal energy is required to disrupt the lattice.