3.1.5: Periodicity: ionisation energies + atomic radii

Question 1

what is the trend in ionisation energies across a period?

Answer 1

there will be a general increase across a period, as the no. of protons in the nucleus increases so there is higher attraction on electrons

Question 2

why does the first ionisation energy decrease between group 2 and 3?

Answer 2

in group 3 the outmost electrons are in p orbitals whereas in group 2 they are is s orbitals, so electrons can be removed easier

Question 3

why does the first ionisation energy decrease between group 5 and 6?

Answer 3

group 5 electrons in the p orbital are single electrons however, in group 6 the outer electrons are paired with some repulsion and, therefore easier to remove.

Question 4

does the first ionisation decrease or increase down a group? why?

Answer 4

decreases; shielding will increase as well as the atomic radius and therefore will have a further distance between outer electrons and nucleus leading to weaker attraction.