electron pair

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Two electrons functioning or regarded as functioning in concert, especially two electrons that form a covalent bond between atoms.
• noun The combination of an electron and a positron as produced by a high-energy photon.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun chemistry, physics Two electrons having opposite spin but all other quantum numbers the same; i.e two electrons in the same atomic orbital or molecular orbital, especially such electrons that function in concert to form a covalent bond