What are the rules that define a semiconductor?

[bluejay27]

Hi,

What are the rules that satisfy which combination of elements are semiconductors?

First one is to satisfy the octet rule to form covalent bond. This can be easily checked by looking at the group number, which is indicative of the number of valence atoms.

The other is the electronegativity
Are there any others?

 

[DrDu]

You already noted in one of the numerous other threads you started on this topic that the octet rule is not always fulfilled in semiconductors like lead sulfide.
From the physical definition, a semiconductor must have a band gap. To be a useful semiconductor, the bandgap should not be too wide. This excludes both strongly covalent and strongly ionic compounds, although e.g. diamond is in some applications considered to be a semiconductor with a wide bandgap.