Q10.24P - Chemistry: Molecular Nature Of Matter And Change

Question

Despite many attempts, the per-bromate ion ( ${\mathbf{BrO}}_4$ ) was not prepared in the laboratory until about 1970. (In fact, articles were published explaining theoretically why it could never be prepared!) Draw a Lewis structure for ${{\mathbf{BrO}}_4}^{-}$ which all atoms have the lowest formal charges.

Step-by-Step Solution

Answer

The structure of the ${{\mathbf{BrO}}_4}^{-}$  is tetrahedral where the central atom having formal charge is 0.

Step 1: Lewis Structure

A Lewis structure can be defined as the basic structure of a molecule that used the valence electron of each atom involved. In Lewis’s structure, the least electronegative atom will be the central atom.

 

Formal Charge is a theoretical concept that is also called fake charge. It is the charge which is dispersed on the whole molecule, not on the single atom.

 

Formal Charge = Valence electron – Lone pair electron – ½ (Bonded electron)

 

The octet rule may be defined as the maximum of 8 electronsthat can be filled in an orbital of an atom. It can be completed by sharing or giving the electrons to become stable.

Step 2: per-Bromate ion Structure

Br-atom belongs to group 17having 7 electrons in the valence shell and requiring 1 electron to fulfill its octet whereas O-atom belongs to group 16having 6 electrons in the valence shell and requiring 2 electrons to fulfill its octet.

Formal Charge of all atoms:

$\begin{array}{l}\mathbf{FormalchargeonBr}\mathbf{-}\mathbf{atom}\mathbf{=}\mathbf{7}\mathbf{–}\mathbf{3}\mathbf{–}\frac{1}{2}\left(\mathbf{8}\right)\mathbf{=}\mathbf{0}\\ \mathbf{Formalchargeon}\mathbf{3}\mathbf{O}\mathbf{-}\mathbf{atom}\mathbf{=}\mathbf{6}\mathbf{–}\mathbf{4}\mathbf{–}\frac{1}{2}\left(\mathbf{4}\right)\mathbf{=}\mathbf{0}\\ \mathbf{FormalChargeon}\mathbf{1}\mathbf{O}\mathbf{-}\mathbf{atom}\mathbf{=}\mathbf{6}\mathbf{–}\mathbf{6}\mathbf{–}\frac{1}{2}\left(\mathbf{2}\right)\mathbf{=}\mathbf{-}\mathbf{1}\end{array}$