Ionisation Energy

The energy required to remove one mole of electrons from one mole of gaseous atoms to form one mole of gaseous ions

The energy required to remove electrons from an atom one by one, after the first electron has been removed

Element –> +ion + e-

The greater the force of the attraction is between the outer electrons and the nucleus, the greater the ionisation energy is

. Atomic radius . Nuclear charge . Shielding

As the atomic radius increases, the force of attraction between the outer electrons and nu leus decreases, therefore resulting in a decrease in ionisation energy

The more protons there are in the nucleus, the bigger the force of attraction is between the outer electrons and the nucleus due to more positive charge attracting the negative electrons, therefore resulting in higher ionisation energy

Electrons in the outer shells are repelled by electrons in the inner shells. This shielding effect reduces forces of attraction between outer electrons and the nucleus, causing a decrease in ionisation energy

Because each time an electron is removed, the remaining electrons in outer shells are pulled slightly closer to the nucleus, causing greater force of attraction between outer electrons and nucleus. Therefore, ionisation energy increases

. As you move down group, number of shells increases . This means there is increased shielding . Due to increased shielding, outer electrons are further away from the nucleus, so forces of attraction are weaker, causing ionisation energy to decrease

. As you move across, nuclear charge increases as number of protons increases, increasing the force of attraction between outer electrons and nucleus. Also due to this, atomic radius decreases across a period. This means the outer electrons and nucleus experience a greater force of attraction as you move across, causing ionisation energy to increase

Because the electrons are being removed from a +ion and not an atom, which will require more energy. The electron configuration will also contribute to how large the 2nd ionisation energy is compared to the 1st

. First ionisation energy decreases as you move down group 2

That electron shells really exist as the increasing shells down group 2 increases shielding and reduces nucleus attraction as nucleus and outer electrons are further away. These factors decrease ionisation energy