The force of attraction is given by:

e²Z/r²

where r is the distance between the electron and the nucleus (covalent radius). e is the charge on an electron. eZ is the charge effective at the electron due to the nucleus and its surrounding electrons.

The quantity Z/r² correlates well with Pauling electronegativities and the two scales can be made to coincide by expressing the Allred-Rochow electronegativity as:

AR=0.744 + 0.359Z/r²

See also: Mulliken scale - Pauling scale