CBSE Class 11-science Answered

                                                    

 

if iodine is dissolved in KI, the triiodide ion I₃^- is formed.
the I₃^- ion has 3 atoms and must be either linear or angular in shape.It is convenient to consider the structure in a series of stages - first an I atom , then I₂ molecule , and then I₃^- ion made up of an I₂molecule with an I^- ion bonded to it by means of a coordinate bond
 I₂ + I ^-→ [ I→I--I ] ^-
Shape is based on a trigonal bypyramid.
To minimise the forces of repulsion three lp occupy the equatorial positions , and I atoms are located at the centre and in the two apical positions.The ion is therefore linear in shape, with a bond angle of exactly of 180°