Draw the Lewis structure for the polyatomic hydroperoxyl (HO2-) anion. Be sure to include all resonance structures that satisfy the octet rule.
Draw the Lewis structure for the polyatomic hydroperoxyl (HO2-) anion. Be sure to include all resonance structures that satisfy the octet rule.
The Correct Answer and Explanation is :
The Lewis structure for the hydroperoxyl anion (HO₂⁻) can be drawn as follows:
1. Count the total number of valence electrons:
- Hydrogen (H): 1 valence electron × 1 atom = 1 electron
- Oxygen (O): 6 valence electrons × 2 atoms = 12 electrons
- The negative charge (⁻) adds 1 extra electron.
So, the total number of valence electrons is:
1 (from H) + 12 (from O) + 1 (from the negative charge) = 14 valence electrons.
2. Draw a skeleton structure:
- Connect the atoms with single bonds. The oxygen atoms are bonded to each other, and one of them is bonded to a hydrogen atom. This forms the basic skeleton: H-O-O.
3. Distribute the remaining electrons:
- After drawing the single bonds (H-O and O-O), each bond accounts for 2 electrons, so 4 electrons are used in the skeleton.
- The remaining 10 electrons are placed around the atoms to satisfy the octet rule.
- Place 6 electrons (3 lone pairs) around the oxygen atoms first. This gives each oxygen atom 6 electrons, and the oxygen in the center gets 2 electrons from the bond with hydrogen.
- Then, place the remaining 4 electrons as lone pairs on the outer oxygen atom.
4. Formal charges:
- To ensure the correct formal charges and minimize them, the oxygen atoms should have negative charges, with the central oxygen bearing a partial negative charge. The overall charge of the molecule is -1.
5. Resonance structures:
There are two possible resonance structures for the hydroperoxyl anion. In both, the bond between the two oxygen atoms can be a single or a double bond, and the lone pairs can be redistributed to maintain octets. The resonance structures are as follows:
- Resonance Structure 1:
- O-H single bond.
- O-O single bond with lone pairs on both oxygen atoms.
- Resonance Structure 2:
- O-H single bond.
- O=O double bond, with one lone pair on the outer oxygen atom.
Explanation:
The hydroperoxyl anion (HO₂⁻) has two oxygen atoms, one of which is bonded to a hydrogen atom, and the other to another oxygen atom. The anion has one extra electron due to its negative charge. The resonance structures arise because of the possibility of shifting the bonding between the two oxygen atoms from a single to a double bond, allowing for the lone pairs on each oxygen atom to be rearranged to minimize formal charges and ensure that the octet rule is satisfied for each atom involved. The negative charge is most commonly localized on the outer oxygen atom, as this helps balance the structure while maintaining overall charge neutrality and stability.