Ionisation Energy

Question 1

What is ionisation?

Answer 1

Ionisation is the removal of one or more electrons

Question 2

Define first ionisation energy

Answer 2

The first ionisation energy is the energy needed to remove 1 electron from each atom in 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions

Question 3

Is ionisation endothermic or exothermic?

Answer 3

You have to put energy in to ionise an atom or molecule, so it’s an endothermic process

Question 4

What state symbol must you use when writing equations involving ionisation energies?

Answer 4

You must use the gas state symbol (g) because the ionisation energies are measured for gaseous atoms

Question 5

What are the factors affecting ionisation energy?

Answer 5

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

Question 6

Explain nuclear charge

Answer 6

The more protons there are in the nucleus, the more positively charged the nucleus is and the stronger the attraction for the electrons

Question 7

Explain distance from the nucleus

Answer 7

Attraction falls rapidly with distance. An electron close to the nucleus will be much more strongly attracted than one further away

Question 8

Explain shielding

Answer 8

As the number of electrons between the outer electrons and nucleus increases, the outer electrons feel less attraction towards the nuclear charge. This lessening of the pull of the nucleus by inner shells of electrons is called shielding (or screening)

Question 9

What does a high ionisation energy mean?

Answer 9

A high ionisation energy means there’s a high attraction between the electron and the nucleus and so more energy is needed to remove the electron

Question 10

What is a successive ionisation energy?

Answer 10

Each time you remove an electron from an atom, there is a successive ionisation energy

Question 11

Define second ionisation energy

Answer 11

The second ionisation energy is the energy needed to remove 1 electron from each ion in 1 mole of gaseous 1+ ions to form 1 mole of gaseous 2+ ions

Question 12

What is the equation for the nth ionisation energy?

Answer 12

X^(n-1)+ ——– X^n+ + e-

Question 13

What do successive ionisation energies show?

Answer 13

Shell structure

Question 14

How do successive ionisation energies show shell structure?

Answer 14

Within each shell, successive ionisation energies increase. This is because electrons are being removed from an increasingly positive ion - there’s less repulsion from the nucleus so they’re held more strongly by the nucleus. The big jumps in ionisation energy happen when a new shell is being broken into - an electron is being removed from a shell closer to the nucleus

Question 15

How can successive ionisation energy graphs show you what group an element belongs too?

Answer 15

Count how many electrons are removed before the first big jump to find the group number

Question 16

How can successive ionisation energy graphs help you predict the electron structure of elements?

Answer 16

Work from right to left, count how many electrons there are before each big jump to find how many electrons are in each shell