What is the oxidation number of each element in kclo3?

##"K" -> +1## ##"O" -> -2## ##"Cl" -> +5##

Wasn't sure which element you were referring to but for a start, ##"K"## and ##"O"## oxidation states are fixed by rules and .

##"Cl"## has variable oxidation states, and can be determined algebraically :

If ##x## is oxidation number for ##"Cl"##, and since no charge overall for the compound, then

##(+1) + x + 3 xx (-2) = 0##

##x - 5 = 0 implies x=+5##