Identify the element having general electronic configuration $ns^2 np^4$ from the following.

$A$ solution of $CrO_5$ in amyl alcohol has a $....$ colour.

How many isotopes of dioxygen are there? Name them.

Given below are two statements $:$
Statement $I : H_2Se$ is more acidic than $H_2Te$.
Statement $II : H_2Se$ has higher bond enthalpy for dissociation than $H_2Te$.
In the light of the above statements,choose the correct answer from the options given below.

The highest catenation ability is shown by

Which of the following statements is incorrect for $H_2SO_4$?