What is the oxidation number of chlorine in naclo4? -1 +7 -5 +1

Na has an oxidation state of +1 whereas O has an oxidation state of -2. The compound is neutrally charged (has no charge) so the sum of all the elements' oxidation states must be zero.

There are 4 oxygen atoms so multiply it's oxidation state by 4:

So

Where X is the oxidation state of chlorine.

1 - 8 = -7

So chlorine must have an oxidation state of +7 in order to cancel the -7 out to get zero.

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