Chemistry · Periodicity

Which of the following best explains why the first ionization enthalpy (ΔH1) for oxygen is lower than that for nitrogen despite oxygen having a higher nuclear charge (Z)?

Verified Solution4 OptionsUpdated: October 2026👁️1 View

1Oxygen has electron pairing in the 2p subshell, causing increased electron-electron repulsion✓
2Nitrogen has completely filled subshells
3Oxygen has a larger atomic radius than nitrogen
4Oxygen has a 2s electron removed which is more penetrating

Correct answer

Oxygen has electron pairing in the 2p subshell, causing increased electron-electron repulsion

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