Final answer:
The Lewis structure for the hydrogen carbonate ion (HCO³⁻) features a central carbon atom with two single bonds and one double bond to oxygen atoms, plus a singly bonded hydrogen atom, with resonance forms alternating the double-bonded oxygen. Hydrogen peroxide (H₂O₂) consists of two oxygen atoms connected by a single bond, each also bonded to a hydrogen atom, with no resonance forms. The correct options are a,b.
Step-by-step explanation:
The student has asked for the Lewis structures for the hydrogen carbonate ion (HCO³⁻) and hydrogen peroxide (H₂O₂), both of which are common components in toothpaste.
Hydrogen carbonate ion (HCO³⁻): Carbon is the central atom, with three oxygen atoms surrounding it - two of these form single bonds with carbon and have additional lone pairs, and one forms a double bond with the carbon atom. The hydrogen atom is attached to one of the singly bonded oxygen atoms.
This ion has one negative charge. The resonance forms of the hydrogen carbonate ion come from the possibility of having the double bond with any one of the three oxygen atoms, resulting in two additional resonance structures.
Hydrogen peroxide (H₂O₂): Each hydrogen atom is singly bonded to an oxygen atom. The two oxygen atoms are then bonded to each other through a single bond with two lone pairs of electrons on each oxygen atom making up the remaining valence electrons.
Hydrogen peroxide does not have resonance structures as the single bonds in the molecule are not interchangeable. The structures of the molecules are critical for understanding the properties and functions of these substances in toothpaste.
For example, hydrogen peroxide serves as a bleaching agent, whereas the hydrogen carbonate ion contributes to the toothpaste's ability to neutralize acids in the mouth, which can help prevent tooth decay. The correct options are a,b.