what is the oxidation number of Pb in Pb(NO3)2
The correct answer and explanation is:
The oxidation number of lead (Pb) in Pb(NO3)2 is +2.
To explain this, let’s break it down:
- Nitrate ion (NO3-): The nitrate ion is a polyatomic ion where nitrogen typically has an oxidation state of +5 and each oxygen has an oxidation state of -2. Since the ion as a whole has a charge of -1, the sum of the oxidation numbers in NO3- must be -1.
- Nitrogen: +5
- Oxygen: -2 × 3 = -6
- Total for NO3-: +5 + (-6) = -1 (which matches the charge on the nitrate ion).
- Lead (Pb): In Pb(NO3)2, there are two nitrate ions, each with a charge of -1. The total negative charge from the nitrate ions is -2 (since -1 × 2 = -2). For the compound to be neutral overall, the total positive charge from lead (Pb) must balance this out. Therefore, the oxidation number of Pb must be +2 to balance the -2 charge from the nitrates.
- Overall charge balance: The compound Pb(NO3)2 is neutral, so the sum of the oxidation numbers must be zero. The lead ion (Pb) has an oxidation number of +2, and the two nitrate ions (NO3-) each contribute a -1 charge, so:
- Pb: +2
- 2 × NO3-: -2
- Total: +2 + (-2) = 0
Hence, the oxidation number of Pb in Pb(NO3)2 is +2. This is consistent with the general rule that lead typically has an oxidation number of +2 in ionic compounds, especially when paired with highly charged ions like nitrate.