Nucleophilic elements in periodic table

[Shannon_McCauley_2D]

Is there a trend in the periodic table that helps distinguish which elements are more nucleophilic? Ex:) I^- is more nucleophilic than Cl^-

[Chem_Mod]

Yes there is a trend. As taken from http://www.chem.ucalgary.ca/courses/351 ... ch8-5.html

Across a row in the periodic table nucleophilicity (lone pair donation) C- > N- > O- > F- since increasing electronegativity decreases the lone pair availability.

If one is comparing the same central atom, higher electron density will increase the nucleophilicity,
e.g. an anion will be a better Nu (lone pair donor) than a neutral atom such as HO- > H2O.

Within a group in the periodic table, increasing polarisation of the nucleophile as you go down a group enhances the ability to form the new C-X bond and increases the nucleophilicity, so I- > Br- > Cl- > F-. The electron density of larger atoms is more readily distorted i.e. polarised, since the electrons are further from the nucleus.