In a $\mathrm{S_N2}$ reaction, a good nucleophile is considered to be willing to donate electrons. So how do we generalize this fact across the periodic table? Does that mean the more electronegative an atom is, the better the nucleophile?

  • $\begingroup$ One should exercise caution in making generalisations across the periodic table. Although related to periodic trends, the extent of an element's nucleophilic character is more complex to determine than using its position in the periodic table. Also keep in mind that as well as atoms, there are other species that are nucleophilic (eg. NH3) and their nucleophilic character is not only based on the properties of the electron donor atom (nitrogen in NH3) but also on the nature of bonding in the species. $\endgroup$ – arevmelikyan Apr 11 '20 at 20:07
  • $\begingroup$ Consider how good a nucleophile F- is $\endgroup$ – Waylander Apr 12 '20 at 7:08

As electronegativity increases the holding capacity of electron by the atom increases. So it is less likely to donate electrons. So we can generalise that access a period in periodic table nucleophilicity decreases.


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