3.1.1.3 Ionisation Energies

Question 1

Define Firtst Ionisation energy?

Answer 1

It is the energy required to remove one elecron from each element in one mole of gaseous atome to form one mole of gaseous 1+ ions
O(g) –> O+(g) + e-

Question 2

What are the three most important things when it come to Ionisation energies?

Answer 2

1. Always use the gas symbol
2. Always refer to one mole rather than a single atom
3. The lower the ionisation energym the easier it is to form a positive ion

Question 3

What are the three main factors that affect ionisation level?

Answer 3

1. Nuclear charge
2. Distance from the nucleus
3. Shielding

Question 4

How does nuclear charge affect ionisation energy?

Answer 4

The more protons in the nucleus, the more attracted an electron will be to the nucleus

Question 5

How does the distance from the nucleus of the electron affect the ionisation energy?

Answer 5

Attraction falls quickly with distance. The further away an electron is the less attracted it is.

Question 6

How does shielding affect ionisation energy?

Answer 6

As the electron number increases, the attraction decreases. This is due to the inner electron shells lessening the force of attraction

Question 7

What is the second ionisation energy?

Answer 7

The amount of energy that is neeeded to remove an electron from each ION in one mole of gaseous 1+ ions.
O+(g) –> O2+(g) + e-

Question 8

What is succesive ionisation energies?

Answer 8

The energy that is required to remove the electrone one after the other.

Question 9

What is the overall trend for ionisation energy (Group 2) as it goes down a group and why?

Answer 9

Decrease
- The atomic radius increases so the outermost electron is further away making the attractive force weaker - less energy is required to remove an electron
- Shielding increases as we go down due to more shells so the attractive forec is weaker - less energy is required to remove an electron

Question 10

What is the overall trend for ionisation energy (Period 3) as it goes across a period and why?

Answer 10

Increase
- As we go across, there is an increase in proton number so there is an increase in nuclear attraction
- Shielding is similar
So more energy is required to remoe the electrons

Question 11

In period 3 what are the exeptions to the increase in ionisation energy?

Answer 11

1. Alunminium and Sulfur
   - The introduction of the P shell in Al causes a higher ionisation energy
   - Additional Shielding to the 3p orbital by the 3s orbital#
2. Phosphorous and Sulfur
   - There is repulsion between two electrons that are in the same orbital in Sulfur, this means that less energy is required to remove the electron