Which element from the following exhibits the highest number of allotropes?

Which of the following is used as a photoconductor in xerox machines?

Determine whether the following statements are True $(T)$ or False $(F)$:
$1.$ $SO_2$ is converted to $SO_3$ in the production of sulfuric acid.
$2.$ Ziegler catalyst is used for the oxidation of $SO_2$ to $SO_3$.

Elements of Group $16$ generally show lower value of first ionisation enthalpy compared to the corresponding periods of Group $15$. Why?

Group $16$ elements are also called:

What is produced by the hydrolysis of one mole of peroxodisulphuric acid $(H_2S_2O_8)$?