The Allred-Rochow scale in chemistry is a measure of electronegativity.

The electrostatic force of attraction between an electron and the nucleus 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

This Electronegativity is often specified as χAR.

As a general rule, the electronegativity increases as one goes across (to the right) and up the Periodic Table.

Alternative scales are called the Mulliken scale and the Pauling scale.

Further Information:

WebElements - Useful definition http://www.webelements.com/webelements/properties/text/definitions/electroneg-allred.html

Chemical properties