Explain why Na, Mg, and Al are good conductors of electricity?

Metals include sodium, magnesium, and aluminum, to name a few. They have metallic bonding, which means that the nuclei of metal atoms are attracted to delocalised electrons, which is a form of attraction.

The transition from sodium to aluminum:

The number of electrons that are delocalized is increasing...
A greater number of electrons is available to transport and carry charge across the structure...
The electrical conductivity rises as a result of this.

I hope this helps you
:)

It is a mixture. simply put, a compound must be pure, that is, of only one chemical structure and composition. a mixture is made of different chemical substances (i.e. elements, molecules, compounds) that are not chemically bonded to each other, but instead physically grouped together, as in the case of gasoline (a homogeneous solution).