Ah, that’s a classic MCQ! The dip at boron is because it has a lower nuclear charge and the electron goes into a new p-subshell, so shielding is higher. For oxygen, it’s because electron-electron repulsion in the paired p-orbital makes removal easier. Honestly, I remember this only because I kept mixing it up with the magnesium-aluminium case while studying under the dim bulb in my orchard’s storage room—the smell of ripe apples made the exceptions stick, yaar.
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