Ionisation energy

Ionisation energy definition

Energy required to remove 1 electron from each atom to form 1 mole of gaseous +1 ions.

which factors increase IE?

Nuclear charge.

Which factors decrease IE?

Electron shielding and atomic radius

IE down a group

DECREASES.

Atomic radius increases (lowers)

Electron shielding increases (lowers)

Nuclear charge increases (increases)

IE across a group

INCREASES.

Atomic radius decreases (lowers)

Electron shielding stays the same

Nuclear charge increases (increases)

IE equations

First: X(g) —> X+(g) + e-

Second: X+(g) —> X2+(g) + e-

Why do s-subshells require more energy than p subshells?

P subshells are further away and kore shielded than s subshells so require less energy to remove an electron.

Why do paired orbitals need less energy to remove electrons?

Paired orbitals repel so need less energy as there is a greater repulsion. More energy is required for single orbitals as theres no energy repelling them.