The typical distance between N and O atoms when they are in a single bond is 136 pm, and 120 pm when they are in a double bond. Which of the following bond lengths would be reasonable for the distance between the N and O atoms in NO2- .
a. 145 pm
b. 136 pm
c. 128 pm
d. 120 pm
Well, it isn't a single bond so you wouldn't expect b. It isn't a double bond so you wouldn't expect d. Since it is between a double and a single bond we wouldn't expect it to be LARGER (not a).
To determine which bond length would be reasonable for the distance between the N and O atoms in NO2-, we need to consider the number of bonds and the typical bond lengths for those types of bonds.
In NO2-, the nitrite ion, there are two oxygen atoms bonded to a central nitrogen atom. Each oxygen atom is connected to the nitrogen atom by a single bond.
The typical distance between N and O atoms in a single bond is 136 pm. Since each oxygen atom forms a single bond with the nitrogen atom in NO2-, we can expect the bond length to be close to 136 pm.
Therefore, the most reasonable bond length for the distance between the N and O atoms in NO2- would be option "a. 145 pm".