A nucleophilic atom is an electron-rich atom in a molecule or ion.  Use the following generalizations to identify the most common types of electron-rich atoms.

1. An atom bearing one or more lone pairs but not a formal positive charge is electron-rich.

eg. 1:

eg. 2:

2. A formally neutral atom bearing a partial negative charge is electron-rich.

eg. 1:

eg. 2:

3. A carbon atom not bearing a formal or partial positive charge and multiple-bonded to another carbon atom is electron-rich.

eg. 1:

eg. 2:

see also electrophilic atom, nucleophile, electrophile