Atomic Structure: Trends in First Ionisation Energy

Ionisation energy is affected by the nucleus’ charge, electron-nucleus distance, and shielding from inner electrons
First ionisation energy decreases within each group, as electrons are further from the nucleus
First ionisation energy increases across a period due to increasing nuclear charge with similar electron-nucleus distance
Successive ionisation energies for one atom reveal shell structure
There’s a significant increase in ionisation energy when removing the first electron from a lower-energy shell, as it is closer to the nucleus.