Answers

2016-03-27T00:30:02+05:30
For BrF5,

[3n1-5] + [3n2-6]

3n-5 is the formula for number of modes of vibration in linear molecule

3n-6 is the formula for number of modes of vibration in non-linear 

combined both because the given molecule is complex(BrF5)

where n= no. of electrons 

where n1= no of electrons in linear (i.e., F & Lonepair in axial)

where n2= no of electrons in non-linear {4 F's in sq.plane}

F has 6e's

=> 3(2+6)-5 + 3(4*6)-6 = 3(8)+3(24)-11 = 24+72-11= 85

Modes of Vibration in BrF5= 85

Similarly,

XeF2{also a complex} trigonal bipyramidal shape 

lone pairs occupying a triangular plane

F's in axial because they're more EN than Lone Pair
=> 3(2*6)-5 + 3(3*2)-6 = 3(12)+3(6)-11= 36+18-11= 63
Modes of Vibration in XeF2=63
For information regarding structures visit  

http://chemwiki.ucdavis.edu/Core/Physical_Chemistry/Spectroscopy/Vibrational_Spectroscopy/Vibrationa...



3 3 3
sorry
http://chemwiki.ucdavis.edu/Core/Physical_Chemistry/Spectroscopy/Vibrational_Spectroscopy/Vibrational_Modes/Number_of_vibrational_modes_for_a_molecule
Above one is the Link