IONISATION ENERGY

definition of ionisation energy

The energy needed to remove 1 electron from each atom in 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions

factors affecting ionisation energy

Nuclear charge, distance from nucleus, shielding

which factors increase ionisation energy

Charge of the nucleus-higher the charge the higher the I.E

which factors decrease ionisation energy

Distance from nucleus, shielding- higher the distance lower the I.E. Increase in shielding, decrease in I.E

trends in first ionisation energy

when you go down a group the I.E decreases. when you go across a period the I.E increases.

why does the I.E decrease down a group

when going down the group each element has an extra electron shell than the one above meaning more sheilding and further away from the nucleus so less attraction and lower I.E

why does the I.E increase across a period

when going across a group the number of protons is increasing meaning stronger nuclear attraction and little shielding resulting in higher I.E