periodicity

• what is meant by ionisation energy?

  the energy required to remove one mole of electrons from one mole of atoms in a gaseous state
• what trend in 1st ionisation energy do you observe within the group of halogen elements?

  as you go down the group ionisation energy decreases
• explain the decreasing trend of ionisation going down a group?

  as you go down the group the outer electrons are further away from the nucleus and are more shielded from the nuclear pull causing less attraction between the nucleus and electrons, making them easier to remove
• what is the first ionisation energy equation?

  E(g) -> E+(g) + e
• explain why the first ionisation energy of sodium is less than that of lithium?

  the outer electron of sodium is further away from the nucleus due to the extra shell of electrons and is more shielded from the nuclear pull, making it easier to remove
• suggest why there is such a large jump in electronegativity when removing from a full shell?

  the electron is removed from a full shell which is closer to the nucleus and is more strongly attracted to the nucleus, requiring more energy to remove