Posted: Sun May 06, 2018 3:42 pm
How does ionisation energy change down and across the periodic table?
Re: Ionisation energy
Posted: Sun May 06, 2018 4:16 pm
The ionisation energy is defined as the energy required to remove an electron from an atom (gas phase). Ionisation energy generally increases on going across a period. This is because on crossing a period, more protons are being added to the nuclei of the atoms. This results in an increase in nuclear charge. The electrons in the outer energy levels will be more tightly held, and more difficult to remove.he first ionisation energy decreases on going down a group. This is because the electron to be removed from the outer energy level is increasingly distant from the nucleus, as a result of the atoms getting bigger. The attraction of the nucleus for the electron becomes less, and it becomes easier to pull it away.