As you know, electronegativity is a property intrinsic to atoms. The application to groups of atoms requires assumptions and linear calculations. In a 1985 JACS paper, John Mullay of Atlas Powder Company presents a simple relation to calculate orbital electronegativity. He has shown that the introduced formalism leads to a total molecular ensemble electronegativity that mirrors empirical measurements more faithfully than total electronegativity equalization. Please see the following:

Calculation of Group Electronegativity

J. Am. Chem. Soc. 1985, 107, 7271-7275.

John Mullay

Contribution from Atlas Powder Company, Atlas Research and Development Laboratory,

Tamaqua, Pennsylvania 18252. Received May 24, 1985

Abstract: A simple relation is presented to calculate orbital electronegativity, viz., x ~= ,xo~ (1 + o.jC,#)6A, + 1.56A,)( where A is the atom being considered, i is the bonding orbital on A that is being considered, x:,~ is the orbital electronegativity of the neutral A atom, 6A,l is the charge on A in orbital i, and the summation is over all bonds to A except i). This equation is a simple modification of a relation presented in an earlier paper. The 6A,I are calculated assuming charge conservation and electronegativity equalization within each bond in the group. If A is the central atom of the group G (e.g., A is C in CH,) and i is the orbital to be bonded then xG = x ~(hA,,) ~= 0 ). It is shown that this formalism leads to group electronegativity values that reproduce empirical trends more faithfully than methods using total electronegativity equalization and at least as well as other methods developed specifically to treat substituent effects.

Hi Tapas,

As you already pointed, electronegativity is a parameter used to describe atomic properties. Electronegativity is therefore related to the ability of atom in a molecule to polarize electron density towards itself. Having said that a molecule may have electronegative atoms, but its electronegativity is not relevant as it is an atomic properties.

One possible definition of electronegativity is related to the mathematical average of ionization energy and electron affinity. A far analogy of these quantities can be found in solids: the anelog of ionization energy can be the work function and an analog of electron affinity can also be found in solids https://en.wikipedia.org/wiki/Electron_affinity#%22Electron_affinity%22_as_defined_in_solid_state_physics. But these are not atomic properties. The mathematical average of these quantities can be used for assessing triboelectrical properties.