In which of the following is the formation of polyanions maximum?

Identify the element having the highest density from the following.

Which of the following statements is incorrect?

Excess of $PCl_{5}$ reacts with concentrated $H_{2}SO_{4}$ to give:

What is formed when ozone reacts with mercury?

Given below are two statements: Statement $I$: The covalency of oxygen is generally two but it can exceed up to four. The oxidation state of oxygen in $SO_2$ is $-2$ and in $OF_2$ it is $+2$. Statement $II$: The anomalous behaviour of oxygen when compared to the other elements of group $16$ is due to its small size and high electronegativity. In the light of the above statements, choose the correct answer from the options given below.