Trends of Period 3 Elements: First Ionisation Energy (AQA A-Level Chemistry): Flashcards

Energy to remove 1 mol $e^-$ from 1 mol gas atoms to $+1$ ions

Generally increases from Na to Ar

Increases (more protons)

No significant increase (same 3rd shell)

Decreases ($e^-$ pulled closer to nucleus)

Outer $e^-$ in p sub-shell (higher energy, more shielded)

Group 2: s sub-shell; Group 3: p sub-shell

$p^4$: 2 $e^-$ in same orbital repel, easier to remove

$p^4$: two $e^-$ paired in same p orbital

↑ nuclear charge, ↓ atomic radius, similar shielding