show the structures of XX3, XX5 and XX7- bent T shape, sq pyramidal, pentagonal bipyramidal
The XX3 compounds have the bent ‘T’ shape, XX5 compounds square pyramidal and IF7 has pentagonal bipyramidal structures.
Example of XX3 is BCl3 --- T shape or trigonal bypiramidal
The central atom Br has 7e I valence shell. 3 of them form electron pair bonds with 3 fluorine atoms leaving behind 4 electron pairs. Thus there are 3 bond pairs and 2 lone pairs (sp2 hybridized). According to VSEPR theory 3 bond pairs occupy corners of the trigonal bypiramidal and the lone pairs occupy the equatorial positions.
Example of XX5 – IF5 – Square pyramidal
The central atom I has 7e in valence shell. 5 of them form electron pair bonds with 5 fluorine atoms leaving behind 1 electron pair (sp3d2 hybridization). Thus there are 5 bond pairs and 1 lone pairs. According to VSEPR this molecule has square pyramidal structure. This leaves four atoms in a plane as a square base and one atom positioned perpendicular (90 degrees) to this plane.
Example of XX7 – IF7 – Pentagonal bipyramidal
As with IF7, application of VSEPR rules suggests seven electron pairs. These are made up from six bonding pairs and one lone pair (sp3d3 hybridization). Hence has unusual pentagonal bipyramidal structure.
