Explore the fascinating world of electronic properties of matter with instructor U. Nithya M.Sc., M.Phil. Learn about polar and nonpolar molecules, polarization of molecules, orientation polarization, electron polarization, atomic polarization, induced polarization, total molar polarization, and dipole moment.
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Polarisation of molecules: when a molcule is placed in an electric field the field polarises it in the three following ways orientation polarisation (Po) Electron polarisation (PE) Atom polarisation (PA)
Orientation polarisation (Po): The electric field tends to align those molecules which possess a permanent dipolement along the directionof the field. This is called orientation polarisation (Po) Debye showed that. 2 4. Po = ------- N [ ----- ] 3 3kT
ELECTRON POLARISATION ( PE): Electron polarisation occurs because the field distorts the electronic cloud of a molecule. n2- 1. M PE = ---------- ----- = [R] n2+ 2. p
ATOMIC POLATISATION (PA): The field distorts the nuclei ( or the atoms) towards the negative end of the field. This is called atomic polarisation (PA). The value of PA= 5 to 10 % of PE
INDUCED POLARISATION(PI): A molecule with induced dipole moment is said to have induced polarisation or distortion or molar polarisation. The induced polarisation is composed of two parts as follows PI= PE+PA
Total molar polarisation : For any molecule the total molar polarisation (P) is equal to the sum of its orientation polarisation and snd its induced polarisation. P= PO+PI Debye derived the following equation Mosotti and clausius related total molar polarisation D - 1. M P = [----------] ------ D+ 2. p
Dipole Moment : The degree of polarity of a molecule is expressed in terms of dipolemoment. It is defined as the product of the mangnitide of one of the charges and the distance between them. = Z x d
Determination by a. Temperature method b. Refractivity method C . Dilute solution method
APPLICATIONS OF DIPOLEMOMENT: 1.Shapes of molecules 2. Distinction between cis trans isomers 3. Dipole moments of linkages 4. Bond angles 5. Presence of resonance 6. Caculation of molecular size 7. To estimate percentage ionic character/ The polarity of a molecule.
