Mulliken defined the electronegativity of an atom as the arithmetic mean of its ionisation energy and electron affinity.
`X_(A)=(1)/(2)(I.P.+E.A.)`
One more relationship given by him, if the values are given in eV is
`X_(A)=("Ionisation potential"+ "Electron affinity")/(5.6)`
When there is pure covalent bond between A-B
`((IP)_(A)+(EA)_(A))/(5.6)=((IP)_(B)+(EA)_(B))/(5.6)`
`implies X_(A)=X_(B)`
When there is formation of `overset(delta-)(A)-overset(delta+)(B)` bond then condition will be
A. `((IP)_(A)+(EA)_(A))/(5.6)gt((IP)_(B)+(EA)_(B))/(5.6)`
B. `((IP)_(A)+(EA)_(B))/(5.6)gt((IP)_(A)+(EA)_(B))/(5.6)`
C. `((IP)_(A)+(EA)_(B))/(2.8)=((IP)_(A)+(EA)_(B))/(2.8)`
D. `((IP)_(A)+(EA)_(B))/(5.6)gt((IP)_(A)+(EA)_(A))/(5.6)`
