Answer:
See below.
Explanation:
Different types of bond models, different interactions of particles in the inner structures.
For sodium metal,
The basic particles, the unit, is metal sodium. So the interaction is originated from metal and metal. We call this interaction, metal, atom-atom interaction.
For sodium chloride,
The basic particles, is 2 different ionic particles, positive particle (sodium, Na+), and negative particle (chloride, Cl-). We call this interaction, ionic-ionic interaction.
So, different interactions, different structures, thus, finally, different binding models.