The formation of the oxide ion, g O from oxygen atom requires first an exothermic and then an endothermic step as shown below: (NEET 2015) o f g g O e O ; H 141kJmol -> o f g g O e O ; H 780kJmol -> Thus, process of formation of O in gas phase is unfavorable even though O is isoelectronic with neon. It is due to the fact that,

The formation of the oxide ion, 2 O g from oxygen atom requires first an exothermic and then an endothermic step as shown below : o 1 f g O e O g ; H 141kJmol -> 2 o 1 f O g e O g ; H 780kJ mol -> Thus, process of formation of 2 O in gas phase is unfavorable even though 2 O is isoelectronic with neon. It is due to the fact that electron repulsion outweighs the stability gained by achieving noble gas configuration. When an electron is added to Oanion, there is strong electrostatic repulsion between the two negative charges. Due to this, the second e