1 Ionisation Energies

Question 1

What is an ionisation energy?

Answer 1

The energy required to remove one mole of electrons from one mole of atoms in the gaseous state.

Question 2

What is ionisation energy measured in?

Answer 2

KJmol¯1

Question 3

What factors effect nuclear attraction? ((3))

Answer 3

• Nuclear Charge
• Electron Shielding
• Atomic radius

Question 4

Explain the effect of the atomic radius on nuclear attraction.

Answer 4

The greater the atomic radius, the smaller the attraction to the nucleus experienced by the outer electrons.

Question 5

Explain the effect of nuclear charge on nuclear attraction.

Answer 5

The more protons in a nucleus means that there is more positive charge, this results in a greater attractive force on the outer electron, however the size of atoms may outweigh this effect.

Question 6

Explain the effect of electron shielding on nuclear attraction.

Answer 6

As the number of electrons between the nucleus and the outer electron increases, the attraction between the nucleus and the outer electron decreases as the inner shell electrons repel the outer shell electrons. More inner shell e- = more e- shielding and less nuclear attraction.

Question 7

What is the general trend of ionisation energies across a period?

Answer 7

There is a general increase in ionisation energies across a period.

Question 8

What is the reasonings for the ‘general increase’ in ionisation energies across a period? ((3))

Answer 8

• The nuclear charge is increasing as there are more protons, this means that there is a stronger attraction between outer electron and the nucleus.
  -Electron shielding is not changing
• Resulting attraction from the outer electron to the nucleus increases and the atom gets smaller

Question 9

What are the anomalies for this general trend? ((2))

Answer 9

• Group 3
• Group 6

Question 10

What is the reasoning behind the anomalies in group 3?

Answer 10

The outer electron from the p orbital is more shielded by the s orbital or in a higher energy level.

Question 11

What is the reasoning behind the anomalies in group 6?

Answer 11

The outer electron is paired in the p orbital, meaning that the like charges repel.