What is the oxidation number of sulfur in #"NaHSO"_4#?
Sodium hydrogen sulfate,
Since you're dealing with a polyatomic ion, you know that the sum of the oxidation states of each individual atom that makes up the anion must add up to give the charge, which in this case is
Oxygen will almost always have an oxidation state of
This means that you have
#overbrace(+1 xx 1)^(color(blue)("one H atom")) + overbrace(ON_"S")^(color(blue)("one S atom")) + overbrace(4 xx (-2))^(color(blue)("four O atoms")) = -1#
#ON_"S" = -1 - 1 + 8 = color(green)(+6)#
The oxidation state of sulfur in sodium hydrogen sulfate is