Final answer:
Resonance structures are alternative Lewis structures that can be drawn for a molecule or ion, showing the movement of electrons. To draw resonance structures, you need to identify the atoms and their connectivity, as well as the lone pairs and formal charges. Then, you can move the electrons around by using arrows to indicate the electron movement. Lastly, you rank the resonance structures from most to least stable based on the formal charges on the atoms involved.
Step-by-step explanation:
Resonance structures are alternative Lewis structures that can be drawn for a molecule or ion, showing the movement of electrons. To draw resonance structures, you need to identify the atoms and their connectivity, as well as the lone pairs and formal charges. Then, you can move the electrons around by using arrows to indicate the electron movement. Lastly, you rank the resonance structures from most to least stable based on the formal charges on the atoms involved.
Here are three examples:
Molecule: Nitrate ion (NO3-)Resonance Structure 1: Nitrogen has 4 bonds and no lone pairs. Oxygen has 1 bond and 2 lone pairs. All atoms have a formal charge of 0. Resonance Structure 2: Nitrogen has 3 bonds and 1 lone pair. One oxygen has a double bond and no lone pairs. The other two oxygen atoms each have 1 bond and 3 lone pairs. All atoms have a formal charge of -1.Resonance Structure 3: Nitrogen has 2 bonds and 2 lone pairs. One oxygen has a double bond and no lone pairs. The other two oxygen atoms each have 1 bond and 3 lone pairs. All atoms have a formal charge of +1.Molecule: Benzene (C6H6)Resonance Structure 1: All carbon and hydrogen atoms have 4 bonds and no lone pairs. All atoms have a formal charge of 0.Resonance Structure 2: All carbon atoms form alternating single and double bonds. All hydrogen atoms have 1 bond and no lone pairs. All atoms have a formal charge of 0.Resonance Structure 3: All carbon atoms form alternating single and double bonds. All hydrogen atoms have 1 bond and no lone pairs. All atoms have a formal charge of 0.Molecule: Carbonate ion (CO32-)Resonance Structure 1: Carbon has 2 bonds and 2 lone pairs. One oxygen has a double bond and no lone pairs. The other two oxygen atoms each have 1 bond and 3 lone pairs. All atoms have a formal charge of 0.Resonance Structure 2: Carbon has 1 bond and 3 lone pairs. One oxygen has a double bond and no lone pairs. The other two oxygen atoms each have 1 bond and 3 lone pairs. All atoms have a formal charge of -1.Resonance Structure 3: Carbon has 3 bonds and 1 lone pair. One oxygen has a double bond and no lone pairs. The other two oxygen atoms each have 1 bond and 3 lone pairs. All atoms have a formal charge of +1.
The student is required to draw resonance structures, calculate formal charges for each atom within these structures, and rank their stability based on the placement and magnitude of charges, with the most stable structures having charges closest to zero.
The question asks to draw additional resonance structures for given molecules, calculate their formal charges, and to rank the stability of these structures. In a Lewis structure, formal charges are assigned by distributing the bonding electrons equally between the bonded atoms. Molecules with resonance have multiple structures that depict possible configurations of electrons, though the actual molecule is a hybrid of these. To compute the formal charge, use the formula: Formal charge = (Valence electrons) - (Non-bonding electrons) - (1/2 Bonding electrons).
Resonance structures are ranked from most to least stable based on the number and placement of charges; structures with charges closest to zero, with negative charges on the more electronegative atoms, and with the least charge separation are generally more stable. The movement of electrons to form different resonance structures is indicated using arrows.