Can one sum the polarizability of atoms?

[mkay]

I'm interested in finding the polarizability of NaCl. Let's say I have the polarizability of $Na^+$ and of $Cl^-$. Can I sum these to get the polarizability of NaCl, that is:

$$\alpha_{NaCl} = \alpha_{Na^+} + \alpha_{Cl^-}$$

Honestly, that does seem very accurate, but perhaps it's to a certain degree..

 

[DrClaude]

That won't work. The polarizability of a molecule depends on properties of the molecular bonds, which bear no relation to the polarizabilities of the constituent atoms.

Values of polarizabilities can be obtained from experiments or by quantum chemistry calculations. I would be very surprised if there were no value available somewhere in the literature.