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Chapter 8: Problem 7

The following ions are best described with resonance structures. Draw the resonance structures, and using formal charge arguments, predict the best Lewis structure for each ion. a. \(\mathrm{NCO}^{-}\) b. \(\mathrm{CNO}^{-}\)

Short Answer

Expert verified
The best Lewis structure for \(\mathrm{NCO}^{-}\) has atoms arranged in the order N-C-O with a triple bond between N and C and a double bond between C and O, having formal charges of -1, 0, and 0 on N, C, and O, respectively. For \(\mathrm{CNO}^{-}\), the best Lewis structure has atoms arranged as C-N-O, with a triple bond between C and N, a single bond between N and O, and a lone pair on O, resulting in formal charges of 0, 0, and -1 on C, N, and O, respectively.

Step by step solution

01

Understand resonance structures

Resonance structures are different possible arrangements of atoms and electrons in a molecule or ion, where the constituent atoms and total charge remain the same, but the arrangement of electrons is different. Resonance structures indicate that the actual structure of the molecule/ ion is a hybrid of these different structures.
02

Understand formal charges

Formal charge is a way to determine the charge on an atom in a molecule or ion, and it depends on the number of valence electrons, the number of electrons surrounding the atom (in lone pairs), and the number of electrons in the bond formation. The formula to calculate the formal charge is: Formal Charge = (Valence Electrons) - (1/2 Bonding Electrons) - (Non-Bonding Electrons) The best Lewis structure is the one with the lowest absolute formal charges on constituent atoms. Now, let's apply these concepts to the given ions.
03

Draw resonance structures for \(\mathrm{NCO}^{-}\)

We want to draw resonance structures of \(\mathrm{NCO}^{-}\). We can have three possible arrangements of the atoms (Z = charge of the ion in each resonance structure): 1. N-C-O-Z 2. N-O-C-Z 3. C-O-N-Z Draw the Lewis structures for these arrangements and calculate the formal charges of the atoms in each resonance structure.
04

Determine the best Lewis structure for \(\mathrm{NCO}^{-}\)

From the resonance structures, determine the one with the lowest absolute formal charges on constituent atoms. That will be the best Lewis structure for \(\mathrm{NCO}^{-}\).
05

Draw resonance structures for \(\mathrm{CNO}^{-}\)

Similarly, we want to draw resonance structures and calculate formal charges for \(\mathrm{CNO}^{-}\). We can have three possible arrangements of the atoms (Z = charge of the ion in each resonance structure): 1. C-N-O-Z 2. C-O-N-Z 3. N-O-C-Z Draw the Lewis structures for these arrangements and calculate the formal charges of the atoms in each resonance structure.
06

Determine the best Lewis structure for \(\mathrm{CNO}^{-}\)

From the resonance structures, determine the one with the lowest absolute formal charges on constituent atoms. That will be the best Lewis structure for \(\mathrm{CNO}^{-}\). Through the above steps, we will have drawn resonance structures for the given ions and determined their best Lewis structures with the help of formal charge arguments.

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Most popular questions from this chapter

Which compound in each of the following pairs of ionic substances has the most exothermic lattice energy? Justify your answers. a. \(\mathrm{LiF}, \mathrm{CsF}\) b. NaBr, NaI c. \(\mathrm{BaCl}_{2}, \mathrm{BaO}\) d. \(\mathrm{Na}_{2} \mathrm{SO}_{4}, \mathrm{CaSO}_{4}\) e. \(\mathrm{KF}, \mathrm{K}_{2} \mathrm{O}\) f. \(\mathrm{Li}_{2} \mathrm{O}, \mathrm{Na}_{2} \mathrm{~S}\)

Write Lewis structures that obey the octet rule for the following species. Assign the formal charge for each central atom. a. \(\mathrm{POCl}_{3}\) e. \(\mathrm{SO}_{2} \mathrm{Cl}_{2}\) b. \(\mathrm{SO}_{4}^{2-}\) f. \(\mathrm{XeO}_{4}\) c. \(\mathrm{ClO}_{4}^{-}\) g. \(\mathrm{ClO}_{3}^{-}\) d. \(\mathrm{PO}_{4}^{3-}\) h. \(\mathrm{NO}_{4}^{3-}\)

Place the species below in order of the shortest to the longest nitrogen- oxygen bond. \(\begin{array}{lllll}\mathrm{H}_{2} \mathrm{NOH}, & \mathrm{N}_{2} \mathrm{O}, & \mathrm{NO}^{+}, & \mathrm{NO}_{2}^{-}, & \mathrm{NO}_{3}^{-}\end{array}\) \(\left(\mathrm{H}_{2} \mathrm{NOH}\right.\) exists as \(\left.\mathrm{H}_{2} \mathrm{~N}-\mathrm{OH} .\right)\)

Two different compounds have the formula \(\mathrm{XeF}_{2} \mathrm{Cl}_{2} .\) Write Lewis structures for these two compounds, and describe how measurement of dipole moments might be used to distinguish between them.

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