Electronegativity , symbol Ï , is a chemical property that says how well an atom can attract electrons towards itself . Electronegativity , symbol Ï ( the Greek letter chi ) , is a chemical property that describes the tendency of an atom or a functional group to attract electrons ( or electron density ) towards itself and thus the tendency to form negative ions . An atom 's electronegativity is affected by both its atomic number and the distance that its valence electrons reside from the charged nucleus .