Chapter 7

Question 1

What is the first ionisation energy ?

Answer 1

The first ionisation energy is the energy required to remove one mole of electrons from one mole of atoms of an element in the gaseous state to form one mole of gaseous 1+ ions

Question 2

What are the factors affecting ionisation energy ?

Answer 2

Generally first ionisation energy increases across a period and decreases down a group
- atomic radius - electrons that are further away from the nucleus are less attracted to the nucleus, therefore a lower ionisation energy
- nuclear charge - this increases with atomic number, meaning there are greater attractive forces between the nucleus and outer electrons, so more energy is required to overcome these forces when removing an electron
- electron shielding - this is when the electrons in full inner shells repel electrons in outer shells meaning outer electrons become less attracted to the nucleus, the greater the shielding the lower the ionisation energy.

Question 3

What is the definition of the second ionisation energy ?

Answer 3

the energy required to remove one mole of electrons from 1 mole of gaseous 1+ ions to form 1 mole of gaseous 2+ ions

Question 4

What are the trends in ionisation energies ?

Answer 4

Question 5

Why is there an increase in ionation energies across period 3