What is polarisation? Discuss it by taking example of lithium.
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Answer:
Polarization -- a partial charge separation induced by a difference in electronegativity between carbon and a heteroatom.
EXAMPLE: Li+ ion(lithium ion) has highest polarising power among the alkali metal ions. Also cations having pseudo-noble gas configurations have higher polarising power due to poor shielding of inner(penultimate) 10 d-electrons and hence greatere effective nuclear charge.
In electrochemistry, polarization is a collective term for certain mechanical side-effects (of an electrochemical process) by which isolating barriers develop at the interface between electrode and electrolyte. These side-effects influence the reaction mechanisms, as well as the chemical kinetics of corrosion and metal deposition.[1]:56 In a reaction we can displace the bonding electrons by attacking reagents. The electronic displacement in turn may be due to certain effects, some of which are permanent (inductive and mesomeric effects), and the others are temporary (electromeric effect). Those effects which are permanently operating in the molecule are known as polarization effects, and those effects which are brought into play by attacking reagent (and as the attacking reagent is removed, the electronic displacement disappears) are known as polarisability effects.