Which choice correctly identifies the oxidation numbers (o.n.) for each element in Ca(NO3)2?

• A. Ca: +1, N: +5, O: -2
• B. Ca: +2, N: +3, O: -2
• C. Ca: +2, N: +5, O: -2
• D. Ca: +1, N: +3, O: -2

Answer: (C)

Verified step by step guidance

1. Step 1: Identify the overall charge of the compound Ca(NO3)2. Since it is a neutral compound, the sum of the oxidation numbers of all atoms must equal zero.
2. Step 2: Assign the oxidation number for calcium (Ca). Calcium is an alkaline earth metal in group 2, so it typically has an oxidation number of +2.
3. Step 3: Assign the oxidation number for oxygen (O) in the nitrate ion (NO3-). Oxygen almost always has an oxidation number of -2 in compounds.
4. Step 4: Let the oxidation number of nitrogen (N) be x. Since there are two nitrate ions, and each nitrate ion has three oxygens, write the equation for the sum of oxidation numbers in one nitrate ion: \(x + 3(-2) = -1\) (because the nitrate ion has a charge of -1).
5. Step 5: Solve the equation for x to find the oxidation number of nitrogen, then verify that the sum of all oxidation numbers in Ca(NO3)2 equals zero by adding the contributions from Ca, N, and O.