In polythionic acid,$H_{2}S_{x}O_{6}$ ($x=3$ to $5$),the oxidation state$(s)$ of sulfur is/are:

$A$ metal ion $M^{3+}$ after the loss of three electrons in a reaction will have an oxidation number equal to

If $HNO_3$ changes into $N_2O$,the oxidation number of nitrogen is changed by

The oxidation number of an element in a compound is evaluated on the basis of certain rules. Which of the following rules is not correct?
$1$. The oxidation number of hydrogen is always $+1$.
$2$. The algebraic sum of all the oxidation numbers of all elements in a compound is zero.
$3$. An element in the free or the uncombined state bears oxidation number zero.
$4$. In all its compounds,the oxidation number of fluorine is $-1$.

The oxidation states of $P$ in $H_{4}P_{2}O_{7}$,$H_{4}P_{2}O_{5}$ and $H_{4}P_{2}O_{6}$,respectively,are:

Consider the following compounds:
$\underline{K}O_2$,$H_2\underline{O}_2$ and $H_2\underline{S}O_4$.
The oxidation states of the underlined elements in them are,respectively,