Question

Explain the shape of $Br{F_5}$ .

Answer 1

To be able to predict the shape of molecules,it is important to learn about the Valence Shell Electron Pair Repulsion Theory,also known as the VSEPR Theory.This theory provides a simple procedure to predict the shape of molecules depending on various factors such as presence of lone pairs around the central atom, number of bonding pairs, repulsive interactions of electron pairs and many more which will be discussed.

Complete step by step answer:
Now we discuss the main postulates of VSEPR theory are as follows:
-The shape of a molecule depends upon the number of valence shell electron pairs (bonded or non-bonded) around the central atom.
-Pairs of electrons in the valence shell repel one another since their electron clouds are negatively charged.
-These pair of electrons tend to occupy such positions that minimize repulsion and thus maximize distance between them.
-The valence shell is taken as a sphere with the electron pairs localizing on the spherical surface at maximum distance from one another.
-A multiple bond is treated as if it is a single electron pair and the two or three electron pairs of a multiple bond are treated as a single super pair.
-Where two or more resonance structures can represent a molecule,the VSEPR model is applicable to any such structure.
-The repulsive interactions of electron pairs decrease in the order: Lone pair-Lone pair > Lone pair-Bond pair > Bond pair-Bond pair.
For the prediction of geometrical shapes of molecules with the help of VSEPR theory,it is convenient to divide molecules into two categories as: (i)molecules in which the central atom has no lone pair and (ii) molecules in which the central atom has one or more lone pairs.
-In the molecule, $Br{F_5}$ ,there is a bromide ion which has a lone pair of electrons and five bond pairs attached to the 5 Fluorine atoms. Hence according to the VSEPR theory, the arrangement of atoms is in an octahedral manner and therefore the shape is predicted to be square pyramidal. Now we can draw the structure of $Br{F_5}$ as,

Note:
The key aspects of the VSEPR theory is important to predict the geometry of a large number of molecules, especially the compounds of p-block elements accurately. It must also be noted that the lone pair electrons occupy more space as compared to the bonding pairs of electrons. Calculating the number of lone pairs and bond pairs and using the tables above is sufficient to predict the shape of a large number of molecules.