module 3: 7.2 ionisation energies

Question 1

define the term first ionisation energy

Answer 1

the first ionisation energy is the energy required to remove one electron from each atom in one mole of gaseous atoms of an element to form one mole of gaseous 1+ ions

Na(g) –> Na+ (g) + e-

Question 2

what are the factors that affect ionisation energy

Answer 2

atomic radium
nuclear charge
electron shielding

Question 3

how does atomic radius affect ionisation energy

Answer 3

The greater the distance between the nucleus and the outer electrons, the less the nuclear attraction.
Increase in distance = less attraction = decrease in ionisation energy

Question 4

how does nuclear charge affect ionisation energy

Answer 4

the more protons there are in the nucleus of an atom, the greater the attraction between the nucleus and the outer electrons meaning smaller atomic radius.
Thus higher ionisation energy

Question 5

how does electron shielding effect ionisation energy

Answer 5

electrons are negatively charged and so inner-shell electrons repel outer-shell electrons. This repulsion, called the shielding effect, reduces the attraction between the nucleus and the outer electrons
Thus decreasing ionisation energy

Question 6

define the term second ionisation energy

Answer 6

the second ionisation energy is the energy requires to remove ONE ELECTRON from each ion in ONE MOLE of gaseous 1+ ions of an element to form one mole of gaseous 2+ ions

Question 7

what do successive ionisation energies allow us to make predictions about

Answer 7

• the number of electrons in the outer shell
• the group of the element on the periodic table
• the identity of an element

Question 8

the trend in first ionisation energy down a group and why

Answer 8

• atomic radius INCREASE
• more inner shells so shielding INCREASE
• nuclear attraction on outer electrons DECREASE
• first ionisation energy DECREASE

Question 9

the trend in the first ionisation energy across a period

Answer 9

• nuclear charge INCREASES
• SAME SHELL have similar shielding
• nuclear attraction INCREASES
• atomic radius DECREASES
• first ionisation energy INCREASES

Question 10

what does a high ionisation energy mean (regarding attraction and energy)

Answer 10

there is a strong attraction between the electron and the nucleus, so more energy is needed to overcome the attraction and remove the electron