Which of the following is not a pseudo-halide ion?

What is the number of oxygen atoms bonded to chlorine in its strongest oxoacid?

Aqua-regia reacts with $Pt$ to yield

An aqueous solution of a halogen salt of potassium reacts with the same halogen $X_2$ to give $KX_3$,a brown-coloured solution,in which the halogen exists as the $X_3^-$ ion,$X_2$ acts as a Lewis acid,and $X^-$ acts as a Lewis base. The halogen $X$ is:

Explain the preparation of chlorine and describe the Deacon's process and electrolytic process for its production.

Which one of the following arrangements does not give the correct picture of the trends indicated against it?