Chemistry

Electronegativity depends on how strongly an atom's nucleus pulls on its valence electrons—a balance between nuclear charge and electron shielding. As you move across the period from C to N to O, the nuclear charge increases (more protons), which pulls electrons closer and increases electronegativity. However, nitrogen has a half-filled $p$ subshell ($2p^3$), which is relatively stable and less "hungry" for additional electrons compared to oxygen's $2p^4$ configuration. Oxygen's greater nuclear charge combined with its need to complete its $p$ subshell makes it pull electrons most strongly, placing nitrogen's electronegativity right in between.

Electronegativity depends on how strongly an atom's nucleus pulls on its valence electrons—a balance between nuclear charge and electron shielding. As you move across the period from C to N to O, the nuclear charge increases (more protons), which pulls electrons closer and increases electronegativity. However, nitrogen has a half-filled $p$ subshell ($2p^3$), which is relatively stable and less "hungry" for additional electrons compared to oxygen's $2p^4$ configuration. Oxygen's greater nuclear charge combined with its need to complete its $p$ subshell makes it pull electrons most strongly, placing nitrogen's electronegativity right in between.