The Inert Pair Effect

Question 1

What is the inert pair effect?

Answer 1

As the group descends, the oxidation state 2 lower than the maximum oxidation state becomes more stable

Question 2

What are the max oxidation states for group 13, 14 and 15?

Answer 2

13 is +3
14 is +4
15 is +5

Question 3

Why is it called INERT pair?

Answer 3

This is the configuration of the lower oxidation state is ns2 and these electrons are not involved in bonding

Question 4

Why does the inert pair effect occur?

Answer 4

-This is because bond enthalpy decreases as you go down the group

Question 5

The lower oxidation state is more favoured as you go down the group. Why do lighter elements favour higher oxidation states compared to heavier elements?

Answer 5

In bonding, energy is required to promote the s electron into hybrid orbitals so they can form bonds

• In lighter elements, this energy is compensated by lots of energy released from strong bonds
• In heavier elements, this energy is not compensated due to less energy released from weaker bonds so formation of higher oxidation states is unfavourable

Question 6

What happens to lattice enthalpy as elements get larger and how does charge affect its value?

Answer 6

Lattice enthalpy will decrease as the element gets larger as Bonds get weaker down the group
More highly charged ions will have a strong attractive and so larger lattice enthalpy

Question 7

Show the order of enthalpy changes in a diagram

Answer 7

Lattice energy for MXn
Atomisation (down)
Electron gain (down)
Ionisation energy (right)
Lattice energy for MXn+2(up)

Question 8

MX + X2 -> MX3

If going to a higher oxidation state is endothermic, does this show the inert pair effect?

Answer 8

Endothermic means it is unfavourable
This demonstrates the inert pair effect is the lower oxidative state is more stable
More energy is required to get to the higher oxidation state than is given back in the formation of the bonds in lattice (weak)

Question 9

MX + X2 -> MX3

If going to a higher oxidation state is exothermic, does this show the inert pair effect?

Answer 9

Exothermic= favourable
This does not show the inert pair effect as X overcomes it
X will have a higher charge density and so the lattice formed will be stronger
This means that more energy is given back in the forming of the lattice bonds than is need to get to the higher ox