Several Lewis structures can be written for perbromate ion, BrO4^-, the central Br with all sing

step 1 Here we're looking at BRO4 minus and we can draw out some resonance structures as well as assign

Several Lewis structures can be written for perbromate ion,...

Several Lewis structures can be written for perbromate ion, $\mathrm{BrO}_{4}^{-}$, the central Br with all single $\mathrm{Br}-\mathrm{O}$ bonds, or with one, two, or three $\mathrm{Br}=\mathrm{O}$ double bonds. Draw the Lewis structures of these possible resonance forms, and use formal charges to predict the most plausible one.

Key Concepts

Octet Rule and Expanded Octet

The octet rule states that atoms tend to gain, lose, or share electrons so as to have eight electrons in their valence shell, which provides stability similar to noble gases. However, elements in periods beyond the second energy level, such as bromine, can accommodate more than eight electrons, forming an expanded octet. This concept is key when evaluating bonding in molecules involving heavier elements.

Formal Charges

Formal charges are calculated for each atom in a molecule using the difference between the number of valence electrons in the free atom and the electrons assigned to the atom in the Lewis structure. They help assess the most plausible Lewis structure by minimizing charges on atoms and ensuring that negative charges reside on more electronegative atoms while positive charges are on less electronegative atoms.

Electronegativity

Electronegativity is the tendency of an atom to attract electrons towards itself. In constructing Lewis structures, it plays an important role in determining the most stable distribution of formal charges, as more electronegative atoms are better able to stabilize negative charges. This helps in choosing between different resonance forms.

Lewis Structures

Lewis structures are diagrams that represent the bonding between atoms of a molecule and the lone pairs of electrons that may exist in the molecule. They provide a way to visualize how atoms share or transfer electrons, and help predict the molecular geometry, bonding interactions, and reactivity of the molecule.

Resonance

Resonance is the concept that some molecules or ions cannot be adequately represented by a single Lewis structure. Instead, multiple valid Lewis structures, called resonance forms, can be drawn. The actual electronic structure is a hybrid of these forms, with the true electron density being delocalized over the molecule, which often contributes to increased stability.

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