Chemistry AS Chapter 7 - Periodicity

Question 1

Define the term first ionisation energy

Answer 1

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

Question 2

What effect does atomic radius have on ionisation energy?

Answer 2

The greater the distance between the nucleus and the outer electrons, the less nuclear attraction. The force of attraction falls of sharply with increasing distance, so atomic radius has a large effect

Question 3

What effect does nuclear charge have on ionisation energy?

Answer 3

The more protons there are in the nucleus of an atom, the greater the attraction between the nucleus and the outer electrons

Question 4

What effect does electron shielding have on ionisation energy?

Answer 4

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 outer electrons

Question 5

Define the term second ionisation energy

Answer 5

The energy required 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 6

What happens to first ionisation energy as the number of shells increases and why?

Answer 6

• Atomic radius increases
• More inner shells so shielding increases
• Nuclear attraction on outer electrons decreases
• First ionisation energy decreases

Question 7

What is the trend in first ionisation energy across a period and why?

Answer 7

• Nuclear charge increases
• Same shell: similar shielding
• Nuclear attraction increases
• Atomic radius decreases
• First ionisation energy increases