Question

Which of the following statements, if true, would support the claim that the NO3− ion, represented above, has three resonance structures? The NO3− ion is not a polar species. A The oxygen-to-nitrogen-to-oxygen bond angles are 90°. B One of the bonds in NO3− is longer than the other two. C One of the bonds in NO3− is shorter than the other two.

Answer 1

Answer:

One of the bonds in nitrate is shorter than the other two.

Explanation:

We would firstly need to draw the Lewis structure for nitrate anion. To do this, let's follow the standard steps:

• calculate the total number of valence electrons: five from nitrogen, each oxygen contributes 6, so a total of 18 from oxygen atoms, as well as one from the negative charge, we have a total of 24 valence electrons;
• assign the central atom, usually this is the atom which is single; in this case, we have nitrogen as our central atom;
• assign single bonds to all the terminal atoms (oxygen atoms);
• assign octets to the terminal atoms and calculate the number of electrons assigned;
• the number of electrons assigned is 24, so no lone pairs are present on nitrogen;
• calculate the formal charges: each oxygen has a formal charge of -1 (formal charge is calculated subtracting the sum of lone pair electrons and bonds from the number of valence electrons of that atom); nitrogen has a formal charge of +2;
• nitrogen doesn't have an octet as well, so we'll both minimize its formal charge and make it obtain an octet if we make one double bond N=O.

Therefore, we may have 3 resonance structures, as this double bond might be formed with any of the 3 oxygen atoms.

By definition, double bonds are shorter than single ones, so one of the bonds is shorter than the other two.