Ionisation Energy

Question 1

What does the process of ionisation produce?

Answer 1

Ions with a positive charge

Question 2

What is ionisation energy?

Answer 2

The energy required to overcome the electrostatic attraction between the positively charged nucleus and the negatively charged electron, which removes an electron the outer shell

Question 3

What is first ionisation energy?

Answer 3

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

Question 4

Factors affecting ionisation energy: Nuclear charge

Answer 4

The more protons in the nucleus, the greater its nuclear charge. The greater the charge, the stronger the nuclear attraction on the outer electron. Therefore a higher nuclear charge means more energy would be needed to overcome the attraction between the nucleus and the outermost electron

Question 5

Factors affecting the ionisation energy: Distance to outermost electron and nucleus

Answer 5

As the distance between the nucleus and electron increases, the attraction between them decreases. The weaker the attraction, the less energy is needed to remove that electron

Question 6

Factors affecting ionisation energy: Electron shielding

Answer 6

Electron shielding is the repulsion between the electron in the different inner shells. This shielding effect reduces the overall nuclear attraction. The more inner shells there are, the greater the shielding effect and the less nuclear attraction experienced by electrons

Question 7

Trend of first ionisation energy down a group

Answer 7

First ionisation energy decreases don’t a group because there are more shells, more shielding effect from inner shell electrons which increases atomic radius. The increases shielding and increased distance from the nucleus outweighs the increasing nuclear charge therefore the nuclear attraction on the outer shell electrons decrease. Less energy needed to remove electron

Question 8

Trend in first ionisation energy across a period

Answer 8

First ionisation energy across shows a general increase because the outer electrons fill the same shell so shielding stays the same, the number of protons increases increasing nuclear charge, atomic radius decreases. Therefore there is a greater nuclear attraction on outer electrons. More energy is needed to remove the outer electron

Question 9

Trend in first ionisation energy across a period exceptions

Answer 9

A general increase but a decrease in two places, from group 2 to 3 and group 5 to 6.

Question 10

Group 2 to 3 first ionisation energy exception reason

Answer 10

P block has a higher energy subshell than the S block, less energy need to remove the electron from the first P block since there’s only one electron.

Question 11

Group 5 to 6 first ionisation energy exception reasoning

Answer 11

Due to the electron pairing in group 6 P orbital, in Group 5 each P orbital contains 1 electron. In group 6, one P orbital contains 2 electrons, paired up. Less energy needed to remove the 2p electron from group 6 due to added repulsion

Question 12

What is successive ionisation energies?

Answer 12

A measure of the energy required to remove each electron in turn

Question 13

Why successive ionisation energies increase with ionisation number?

Answer 13

Once an electron have been removed, there are the same number of protons but fewer electrons, so proton:electron ratio increases. Remaining electrons are more strongly attracted to the nucleus. More energy needed to remove each electron in turn