Mobile electrons?

Question

Which of the following solids has electrons that are mobile, and how do you know? Potassium iodide, camphor, zinc, silicon dioxide

Answer 1

Zinc.

It's a metal and thus has molecular orbitals delocalized throughout the solid that can convey electrons with a small amount of energy. This explains its good thermal and electrical conductivities.

And, there do exist conductive organic polymers!

Hope this helps you!

Answer 2

Only metals have freely moving electrons, so the answer is zinc.