The positive charge that an electron experiences from the nucleus, equal to the nuclear charge but reduced by any shielding or screening from an intervening electron distribution. The core electrons lie between the nucleus and the valence electrons resulting in partial shielding of the nuclear charge. Filling the 3d and 4f orbitals for the first time results in a large increase in effective nuclear charge. The ease with which an electron can be removed from an atom in the gas phase. Also at group 16 due to repulsion term in electron pairing i.e. n p 4 n p 3 .
IEs increase progressively for a particular element.
Energy released on adding an electron to an atom in the gaseous state to form a negative ion. Irregularities at group 2 since these have a filled n s 2 shell and do not form stable negative ions. As expected this means than group 15 elements have very low electron affinities due to disruption of the half filled n p 3 shell. The power of an atom in a molecule to attract electrons to itself. Electronegativity is not a property of an isolated atom, rather it is dependent on the nature and environment of an atom in a molecule.