Question

calculate the oxidation state of Cl in Chlorine gas

Answer 1

Explanation:

The oxidation number of chlorine can be -1, 0, +1, +3, +4, +5, or +7, depending on the substance containing the chlorine.

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But chlorine can have other oxidation numbers, for example:

+1 in NaClO.

+3 in NaClO2.

+4 in ClO2.

+5 in NaClO3.

+7 in NaClO4.

Answer 2

oxidation number of chlorine can be -1, 0, +1, +3, +4, +5, or +7, depending on the substance containing the chlorine.
...
But chlorine can have other oxidation numbers, for example:
+1 in NaClO.
+3 in NaClO2.
+4 in ClO2.
+5 in NaClO3.
+7 in NaClO4.