7.2 Ionisation Energy

Energy required to remove one electron from each atom in one mole of gaseous atoms of an element to form one mole of gaseous 1+ ions

Na (g) ——> Na+ (g) + e-

Na+ (g) ——> Na 2+ (g) + e-

Cl (g) ——> Cl+ (g) + e-

Atomic radius Nuclear charge Electron shielding

Greater the distance between nucleus and outer electrons, less nuclear attraction Less attraction means lower ionisation energy

More protons in a nucleus of an atom, greater the attraction between nucleus and outer electrons Greater attraction means higher ionisation energy

Electrons are negatively charged and inner shell electrons repel outer shell electrons This repulsion is the shielding effect Reduces attraction between nucleus and outer electrons - lower ionisation energy

After the first electron is lost, the other electrons are attracted more strongly to the nucleus More ionisation energy is required to remove the other electrons

Energy required to remove one electron from each ion in one mole of gaseous 1+ ions of an element to form one mole of gaseous 2+ ions

Large increase in ionisation energy The shell is closer to the nucleus, and there is less shielding, so greater ionisation energy

It increases, due to increasing nuclear charge

It decreases, due to increasing atomic radius

Boron has no electrons in the 2p sub shell, but Beryllium has an electron in the 2p sub shell, which is further away from the nucleus, so less energy is released.

In Oxygen, there is a paired orbital in the 2p sub shell, so there is repulsion from the other electron, which means it’s easier to remove the electron, than in Nitrogen