polarizability of an element

[bijal]

can anyone please explain the meaning of polarizability of an element along with it's unit of measurement and an explaination on how the unit has been deived.
thanks.

[Dan the Chemist]

An atom or ion is described as being polarisable, or having a high polarisability if the electron density around it is easily deformed.

Generally, polarisable atom/ions are (a) big and (b) have low electronegativity (which implies low charge)

For example, Mercury (Hg) is very polarisable.

Polarisable atoms or ions are also referred to as 'soft'.

Ions are described as polarisING if it strongly induces the polarisation of other atoms/ions.

Generally, polarising ions are (a) Small (b) Highly charged

I can't help you on the quantitative side of things though, sorry.