Write resonance structures for each of the following ions. (a) NO2^- ; (b) BrO3^- ; (c) PO4^3-.

Write resonance structures for each of the following ions....

Write resonance structures for each of the following ions. (a) $\mathrm{NO}_{2}^{-} ;$ (b) $\mathrm{BrO}_{3}^{-} ;$ (c) $\mathrm{PO}_{4}^{3-}$. (Hint: Consider both the $\mathrm{Br}$ and the $\mathrm{P}$ to share more than an octet of electrons in order for them to also form at least one double bond.)

Write resonance structures for each of the following ions. (a) $\mathrm{NO}_{2}^{-} ;$ (b) $\mathrm{BrO}_{3}^{-} ;$ (c) $\mathrm{PO}_{4}^{3-}$. (Hint: Consider
both the $\mathrm{Br}$ and the $\mathrm{P}$ to share more than an octet of electrons in order for them to also form at least one double bond.)

Key Concepts

Formal Charge

Formal charge is a calculated value assigned to each atom in a molecule based on the difference between the number of valence electrons in the free atom and the number of electrons assigned to it in the Lewis structure. It is an important factor in evaluating the stability of different resonance forms, where structures with minimized formal charges tend to be more favorable.

Lewis Structures

Lewis structures are diagrams that represent the bonding between atoms within a molecule or ion and the distribution of valence electrons, including lone pairs. They serve as the foundation for constructing resonance forms by providing a schematic view of how electrons may be rearranged while maintaining the overall connectivity of the atoms.

Resonance Structures

Resonance structures are different Lewis structural representations of a molecule or ion that show the delocalization of electrons. They are used to depict the idea that the actual electron distribution is a hybrid of several possible configurations, contributing to the overall stability and reactivity of the species.

Expanded Octet

Expanded octet refers to the ability of atoms in the third period and beyond (such as phosphorus and bromine) to accommodate more than eight electrons in their valence shell. This concept is critical when drawing resonance structures for certain ions, as it allows these atoms to form additional bonds or double bonds, facilitating a more stable electron distribution.

Transcript

00:01 Bonds are just forces that are able to hold atoms together to make molecules and compounds.

00:04 A few different types of these chemical bonds, ionic bonds, polar covalent and covalent bonding.

00:11 So here we're looking at resonance structures.

00:13 So this is where we have formal negative and formal positive charges perhaps, and we are able to delocalize electrons throughout the whole molecule.

00:22 So this does have a stabilizing effect.

00:25 So for example, we've got no2 minus.

00:29 So we've got oxygen, nitrogen, oxygen.

00:34 We have one minus charge overall.

00:43 And this is in resonance with the following.

00:53 Where we have shifted the electron density.

00:59 And so in the next example, we have quite a few resonance structures.

01:04 We've got three to look at here with br 03 minus.

01:08 We've got bromine, double bond oxygen, double bond oxygen, single bond oxygen.

01:15 So the single bond oxygen is where that negative charge will sit.

01:20 This is in resonance of the following, which is also in resonance with the following.

01:35 We're just moving the location of the double bond as we move about the formal negative charge.