Looking at the periodic table, group II elements like magnesium are known to be metallic, and yet they have full outer shells. So this means they should have full (valence) bands.
Now, last time I checked a completely full band does not conduct.
In a similar way, group IV elements like silicon, germanium, and tin (which is practically a metal!) are actually semiconductors. But, diamond is an insulator.
I am an undergraduate of physics (and a newcomer to this site). I would love to understand the resolution to this problem. I have just started learning solid state physics so my knowledge is somewhat limited.
Why do group II elements conduct and group IV elements not act like semiconductors?
Why do people keep using "Fermi energy" and "Fermi level" interchangeably?