How many isomers of $$\mathrm{C}_4 \mathrm{H}_{11} \mathrm{~N}$$ are tertiary amines?

Which element from following exhibits diagonal relationship with $$\mathrm{Mg}$$ ?

Identify the good conductor of electricity from following band gap energy values of solids.

Identify the product obtained when ethoxybenzene reacts with hot and concentrated $$\mathrm{HI}$$.