Why is conductivity increasing across the periodic table from sodium to magnesium to aluminium?

Answer 1

Explanation of this trend

For an element to conduct electricity, it must contain electrons that are free to move. In general, metals are good conductors of electricity and non-metals are poor conductors of electricity.

Sodium, magnesium and aluminum

Sodium, magnesium and aluminum are all metals. They have metallic bonding, in which positive metal ions are attracted to delocalised electrons. The delocalised electrons are free to move and carry charge. Going from sodium to aluminum:

• the number of delocalised electrons increases ...
• there are more electrons which can move and carry charge ...
• so the electrical conductivity increases.

Answer 2

Aluminium has a greater number of electron shells and larger atomic radius, meaning that its pull on its outer electrons is less, meaning that they can flow more easily. Also, it has more electrons on its outer shell (3, rather than 1 or 2) meaning that there are more electrons to flow.