Which from the following solids exhibits isotropic properties?

Which of the following acts as an intrinsic semiconductor?

Explain the following with suitable examples:
$(v)$ $12-16$ and $13-15$ group compounds.

Classify each of the following solids as ionic,metallic,molecular,network (covalent) or amorphous.
$(i)$ Tetra phosphorus decoxide $(P_{4}O_{10})$ $(ii)$ Ammonium phosphate $(NH_{4})_{3}PO_{4}$
$(iii)$ $SiC$ $(iv)$ $I_{2}$ $(v)$ $P_{4}$ $(vi)$ Plastic $(vii)$ Graphite $(viii)$ Brass $(ix)$ $Rb$ $(x)$ $LiBr$ $(xi)$ $Si$

Heating steel to bright redness and then cooling suddenly by plunging it into oil or water,makes it

$p$-type and $n$-type semiconductors are formed due to