$4-$ Explain different atomic bonding and give an example for each category of bonding. Describe bonding energy between atoms using a graph and formula. How is thermal expansion related to the bonding energy?

$5-$ What are the effects of doping concentration on the electrical conductivity of an extrinsic semiconductor? What must be done to an intrinsic semiconductor to turn it into an $"N-$type" semiconductor? In extrinsic semiconductors, what are majority carriers and how do they differ from minority carriers?