The Lewis structure for NO3- (nitrate ion) involves resonance, meaning there are multiple valid structures. Here's how to draw one:
1. Count valence electrons: N has 5, each O has 6, and there's an extra electron from the negative charge (5 + 6
3 + 1 = 24).
2. Central atom: Nitrogen is the least electronegative, so it goes in the center.
3. Single bonds: Connect each oxygen to the nitrogen with a single bond (3 bonds use 6 electrons).
4. Remaining electrons: Distribute the remaining 18 electrons (24 - 6 = 18) as lone pairs on the oxygens. Each oxygen gets 3 lone pairs (6 electrons each), giving you a total of 18.
5. Formal charges: Calculate the formal charge on each atom: N has 5 - 0 - (8/2) = +1, and each O has 6 - 6 - (2/2) = -1.
6. Resonance: The negative charges can be distributed to the other oxygens, so there are three possible resonance structures.