Q32Short answer
Nitrogen has positive electron gain enthalpy whereas oxygen has negative. However, oxygen has lower ionisation enthalpy than nitrogen. Explain.
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The outermost electronic configuraton of nitrogen (2s2 2px1 2py1 2pz1) is very stable because p-orbital is half filled. Addition of extra electron to any of the 2p orbital requires energy. Oxygen has 4 electrons in 2p orbitals and acquires stable configuration i.e., 2p3 configuration after removing one electron.