Ionisation energy of the Periodic Table elements
The first ionisation energy is the energy required to remove one mole of the valence electrons from one mole of gaseous atoms to produce 1 mole of gaseous ions each with a charge of 1+. This is more easily seen in symbol terms. X --> X+ + e It is the energy needed to carry out this change per mole of X. Suggest how the ionisation energy changes across Period 3 and down Group 17 of the Periodic Table.