The melting temperature increases from sodium to aluminum due to the stronger metallic bonding in aluminum, which has a higher number of delocalized electrons compared to sodium. While sodium has a simpler structure with weaker ionic interactions, aluminum's more complex arrangement leads to greater stability and higher melting points. The discussion emphasizes the importance of understanding the role of ions in metallic bonding, despite initial confusion about their relevance. The markscheme indicates that ions should be considered in the explanation, reinforcing the connection between atomic structure and melting temperature. Ultimately, the relationship between atomic structure and melting points is crucial for a comprehensive understanding of the topic.
