What is the oxidation number of oxygen in Na₂O?

Question

Quizplus · Accepted Answer

To determine the oxidation number of oxygen in a compound, we need to assign the oxidation numbers for the other elements first. 
Here, we can assign the oxidation number of sodium, sulfur, and boron based on their usual oxidation numbers. Sodium has a +1 oxidation number, sulfur has a -2 oxidation number, and boron usually has a +3 oxidation number. 
Now, let x be the oxidation number of oxygen. 
The sum of oxidation numbers in a compound should equal its overall charge, which is 0 in this case. 
So, we have:

(+1) + (-2) + 12(+3) + x + (-2) + x = 0

Simplifying the expression, we get:

+7x + 33 = 0

Solving for x, we get x = -33/7, which is approximately -4.71.

Since the oxidation number should be a whole number, the closest option is -2, which is Choice C.

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What Is the Oxidation Number of Oxygen in Na₂O