Question

which statement best compares the melting points of magnesium and sodium?
sodium has a higher melting point because it contributes one fewer
electron per atom than magnesium in the electron sea.
sodium has a higher melting point because it contributes two
electrons per atom than magnesium in the electron sea.
magnesium has a higher melting point because it contributes one
additional electron per atom than sodium in the electron sea.
magnesium has a higher melting point because it contributes two
additional electrons per atom than sodium in the electron sea.

Explanation:

Metals have metallic bonding. In metallic bonding, atoms contribute electrons to the electron sea. Magnesium (\(Mg\)) has a higher melting point than sodium (\(Na\)). Sodium is in Group 1 and has 1 valence electron per atom, so it contributes one electron to the electron sea. Magnesium is in Group 2 and has 2 valence electrons per atom, so it contributes two electrons to the electron sea. More electrons in the electron sea lead to stronger metallic bonding. Stronger metallic bonding requires more energy to break, resulting in a higher melting point.

Answer:

Magnesium has a higher melting point because it contributes two additional electron per atom than sodium in the electron sea.