Ionisation energies

Question 1

The Ionisation Energy (IE) of an element is the

Answer 1

amount of energy required to remove one mole of electrons from one mole of gaseous atoms of an element to form one mole of gaseous ions

Question 2

Ionisation energies are measured under standard conditions which are

Answer 2

298 K and 101 kPa
The units of IE are kilojoules per mole (kJ mol-1)

Question 3

The first ionisation energy (IE1) is the

Answer 3

s the energy required to remove one mole of electrons from one mole of atoms of an element to form one mole of 1+ ions

E.g. the first ionisation energy of gaseous calcium:
Ca(g) → Ca+ (g) + e- IE1 = +590 kJ mol-1

Question 4

Ionisation energies show …………. - a trend across a period of the Periodic Table

Answer 4

periodicity

Question 5

As could be expected from their electron configuration, the group 1 metals have a relatively low ionisation energy, whereas the noble gases have very high ionisation energies

The size of the first ionisation energy is affected by four factors:

Answer 5

Size of the nuclear charge

Distance of outer electrons from the nucleus

Shielding effect of inner electrons

Spin-pair repulsion

Question 6

First ionisation energy………. across a period and …………. down a group

Answer 6

increases

decreases