Find out the oxidation number of chlorine in the following compounds and arrange them in increasing order of oxidation number of chlorine.
$NaClO_4, NaClO_3, NaClO, KClO_2, Cl_2O_7, ClO_3, Cl_2O, NaCl, Cl_2, ClO_2$.
Which oxidation state is not present in any of the above compounds?

(N/A) The oxidation numbers are calculated as follows:
$NaCl: Cl = -1$
$Cl_2: Cl = 0$
$NaClO: +1 + Cl - 2 = 0 \implies Cl = +1$
$Cl_2O: 2Cl - 2 = 0 \implies Cl = +1$
$KClO_2: +1 + Cl + 2(-2) = 0 \implies Cl = +3$
$ClO_2: Cl + 2(-2) = 0 \implies Cl = +4$
$NaClO_3: +1 + Cl + 3(-2) = 0 \implies Cl = +5$
$ClO_3: Cl + 3(-2) = 0 \implies Cl = +6$
$NaClO_4: +1 + Cl + 4(-2) = 0 \implies Cl = +7$
$Cl_2O_7: 2Cl + 7(-2) = 0 \implies Cl = +7$
Increasing order of oxidation number of $Cl$:
$NaCl (-1) < Cl_2 (0) < NaClO/Cl_2O (+1) < KClO_2 (+3) < ClO_2 (+4) < NaClO_3 (+5) < ClO_3 (+6) < NaClO_4/Cl_2O_7 (+7)$
The oxidation state $+2$ is not present in any of the above compounds.