In the compound NH3, what is the oxidation number of nitrogen?

• A. +3
• B. +5
• C. -3
• D. 0

Answer: (C)

Verified step by step guidance

1. Recall that the oxidation number is a hypothetical charge assigned to an atom in a molecule, assuming that electrons in all chemical bonds are assigned to the more electronegative atom.
2. Identify the oxidation number of hydrogen in NH3. Since hydrogen is less electronegative than nitrogen, hydrogen is assigned an oxidation number of +1.
3. Let the oxidation number of nitrogen be x. Since there are three hydrogen atoms, the total oxidation number contribution from hydrogen is 3 × (+1) = +3.
4. Write the equation for the sum of oxidation numbers in the neutral molecule NH3, which must equal zero: \(x + 3(+1) = 0\).
5. Solve the equation for x to find the oxidation number of nitrogen: \(x + 3 = 0 \Rightarrow x = -3\).