Answer :
Final answer:
The nitrate ion has three resonance structures, fractional bond orders of 4/3 for the N-O bonds, a formal charge of +1 on nitrogen and -2/3 on each oxygen, an overall charge of -1, and a trigonal planar geometry with bond angles of approximately 120 degrees.
Explanation:
The nitrate ion (NO3-) is characterized by a few specific features in its Lewis structure and bonding:
- The nitrate ion has three resonance structures, and all N-O bonds are equivalent, which is represented by a fractional bond order of approximately 4/3, implying that the bonds are neither purely single nor double but an average of these.
- In nitrate, the nitrogen atom has a formal charge of +1 and the oxygen atoms have an effective formal charge of -2/3 each. This is consistent with the observation that the N-O bonds are equal in length.
- The overall charge of the nitrate ion is -1, which is due to the presence of an extra electron in the system.
- The geometry around the nitrogen atom is trigonal planar, with bond angles of approximately 120 degrees.
It is important to note that while formal charges help us understand the distribution of electrons in the molecule, they are different from oxidation numbers, which are used to track electron transfer in redox reactions.
LibreTexts™ mentions that in the actual structure of the nitrate ion, the electrons are spread evenly across all three N-O bonds. The depiction often includes dashed lines to represent these fractional bonds.
