Question

These species do not obey the octet rule. Draw a Lewis structure for each, and state the type of octet-rule exception:

(a)${\mathbf{BrF}}_3$

(b)${{\mathbf{ICl}}_2}^{-}$

(c)${\mathbf{BeF}}_2$

Short answer

The Lewis structure ofthis moleculedoes not follow but they form the stable molecule. These are exceptions or drawbacks of the octet rule.

(a) ${\mathbf{BrF}}_3$=Trigonal Planar structure.

(b) ${{\mathbf{ICl}}_2}^{-}$=distorted trigonal pyramidal structure.

(c) ${\mathbf{BeF}}_2$= Tetrahedral structure.

Step-by-step solution

Lewis Structure

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

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

Some molecules are formed violating the octet rule because of the energy evolved by the formation and breaking of the bond. The energy released while forming a bond is called bond energy and the higher the bond energy, the stronger the bond.

Explanation

Br-atom belongs to group 17 having 7 electrons in the valence shell andrequires 1 electron to fulfil the octet whereas F-atom belongs to group 17having 7 electrons in the valence shell and 1 electron required to fulfil the octet.Br-atom canaccommodate more electrons because of the empty d-orbital.

Clarification

I-atom belongs to group 17having 7 electrons in the valence shell andrequires 1 electron to fulfil octet whereas Cl-atom belongs to group 17having 7 electrons in the valence shell andrequires 1 electron to fulfil octet. In Lewis’s structure, the I-atom can accommodate more electrons because of the empty d-orbital.

Simplification

Be-atom belongs to group 2 having 4 electrons in the valence shell andrequires 4electrons to fulfil the octet, F-atom belongs to group 17having 7 electrons in the valence shell and 1 electron required to fulfil the octet. In Lewis’s structure, the Be-atom is bonded with 2 f-atom. Be-atom is electron deficient as it does not have enough energy to accommodate more electrons.