Periodicity

Question 1

What 3 factors affect the value of ionisation energies?

Answer 1

nuclear charge

atomic radius

electron shielding

Question 2

Define first ionisation energy

Answer 2

the energy required to remove 1 mole of electrons from 1 mole of gaseous atoms to form one mole of gaseous plus one ions.

Question 3

What are successive ionisation energies?

Answer 3

a measure of the amount of energy required to remove each electron in turn.

Question 4

Why is each successive ionisation energy higher than the one before?

Answer 4

This is because there will be a smaller atomic radius and the positive nuclear charge will outweigh the negative charge.

Question 5

Explain the trend of ionisation energies across a period.

Answer 5

Ionisation energies generally increase.

nuclear charge increases

shielding stays the same

atomic radius decreases because electrons are added to the same shell so the outer shell is draw inwards slightly.

Question 6

What are the trends down a group?

Answer 6

First ionisation energy decreases

atomic radius increases

shielding increases

nuclear charge increases but other 2 factors outweigh this.

Question 7

Why do group 3 elements have a lower ionisation energy than group 2?

Answer 7

This is because group 3 elements have their outer electrons in a p orbital whereas group 2 elements have theirs in a s orbital and p orbitals have a slightly higher energy than s orbitals and a re slightly further away from the nucleus making them easier to remove.

Question 8

Why do group 6 elements have a lower ionisation energy than group 5?

Answer 8

This is because in group 5 elements each of the p orbital only contain one electron whereas in group 6, the outermost electron is spin paired in the p orbital. Electrons that are spin paired experience some repulsion making it easier for them to be removed.

Question 9

How does atomic radius affect ionisation energies?

Answer 9

The larger the atomic radius, the smaller the nuclear attraction experienced by the outer electrons.

Question 10

How does nuclear charge affect ionisation energies?

Answer 10

The higher the nuclear charge, the larger the attractive force on the outer electrons.

Question 11

How does the electron shielding affect ionisation energies?

Answer 11

Inner shells of electrons repel the outer shell electrons because they are all negative. Hence, the more shielding, the smaller the nuclear attraction experienced by other electrons.