Answer:
Explanation:The formation of the oxide ion, O
2−
(g), from oxygen atom requires first an exothermic and then an
endothermic step as shown below:
O(g)+e
−
→O
−
(g);Δ
f
H
⊖
=−141kJmol
−1
O
−
(g)+e
−
→O
2−
(g);Δ
f
H
⊖
=+780kJmol
−1
Thus, process of formation of O
2−
in gas phase is unfavourable even though O
2−
is isoelectronic with neon. It is due to the fact that:
