determining polarizability!

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Shelbyhamilton 3H
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Joined: Fri Sep 26, 2014 2:02 pm

determining polarizability!

Postby Shelbyhamilton 3H » Mon Mar 02, 2015 10:16 pm

in Introduction to Organic Chemistry, question 4.1 A self test asks which is more nucleophilic, CI- or I-. I understand the correlation between polarizability and nucleophillic-ness, but I thought a molecule was more polarizable the larger it was?

but here I- is smaller and more polarizable!

Thank you-
shelby hamilton

Niharika Reddy 1D
Posts: 127
Joined: Fri Sep 26, 2014 2:02 pm

Re: determining polarizability!

Postby Niharika Reddy 1D » Mon Mar 02, 2015 11:21 pm

Your association between size and polarizablility is correct (larger=more polarizable)

However, I- is larger than Cl-, not smaller.
As you go down a group in the periodic table, the atomic radius increases as shielding increases and the increased number of electrons are more loosely bound to the nucleus. Anions are generally larger than their respective neutral atoms because adding an electron increases electron-electron repulsion.

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Re: determining polarizability!

Postby Chem_Mod » Tue Mar 03, 2015 1:05 am

Niharika is correct, iodide is much bigger. Since it is lower on the periodic table it simply has more orbitals (principal quantum number n=5, whereas chlorine n=3).

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