A novel connectivity index of valence shell electron energy levels for a ground state atom ^mVEI (m=0, 1, 2, …) is put forward in this paper, which appears uniquely to the ground state atom and has excellent structural selectivity. Regarding ^0VEI, ^1VEI, total ionization energy of valence shell electrons ΣniEi and total valence shell electrons Σni as fundamental parameters, the electronegativity of element can be defined as follows: X~N=0.444067+1.190653(1-1. 32775/Σni)(^0VEI)- 3.154675(^1VEI)+0.134591(ΣniEi/Σni). By above formula the electronegativities of maingroup elements, subgroup elements and inert elements in the Periodic Table are given. The results indicate that the new electronegativity scale X~N is in conformity very much with the Pauling scale which is widely accepted. Moreover, electronegativities of hybridrized orbitals sp, sp^2, sp^3 for carbon atom can be also obtained from the connectivity index of valence orbital energy levels.

Key words: GROUND STATE, CARBON ATOM, HYBRID ORBITAL, ATOM, ELECTRON ENERGY LEVEL, ELECTRONEGATIVITY