Which of the following dopants is added to silicon to obtain an $n$-type semiconductor?

Soldiers of Napoleon's army while at the Alps during a freezing winter suffered a serious problem regarding the tin buttons of their uniforms. White metallic tin buttons got converted to grey powder. This transformation is related to

Which of the following exists as covalent crystals in the solid state?

Write a note on the classification of materials based on their conductivity.

Which of the following oxides shows electrical properties like metals?

Classify the following solids in different categories based on the nature of intermolecular forces operating in them:
Potassium sulphate,tin,benzene,urea,ammonia,water,zinc sulphide,graphite,rubidium,argon,silicon carbide.