Ionisation Energies

Question 1

What is the definition of ionisation energy?

Answer 1

Energy required to remove 1 mol of electron from 1 mol of gaseous atoms

Question 2

What is second ionisation energy?

Answer 2

Energy required to remove 1 mol of electron from a 1+ ion

Question 3

What are the 3 factors affecting ionisation energy?

Answer 3

1. Size of nuclear charge, how many protons are there, more protons means more force or attraction
2. Nuclear attraction to electron, inner shell repels outer shells
3. Sheilding/ Atomic radius, larger Atomic radius, means less energy needed to remove electrons

Question 4

Explain why there is a general increase in ionisation energy across the periods?

Answer 4

1. Nuclear charge increases
2. Electrons added to same shell
3. Greater attraction to outermost electron to the nucleus
   more energy required to remove electron

Question 5

What 2 adjacent elements are exceptions in period 2? and why?

Answer 5

1. Oxygen and Nitrogen
2. Electron in Oxygen is spin pairing, in O this spin pairing leads to repulsion so less energy is required to remove an electron

Question 6

What are the exceptions in ionisation energies between Beryllium, Boron and Magnesium, Aluminium?

Answer 6

1. Both Be and Mg have a higher ionisation energies than elements after in the period
2. This is because Al and B have their outer electron its own sub shell so less energy is needed to remove, whereas Be and Mg electron is paired so need more energy to remove it.

Question 7

Write an equation to represent the fourth ionisation energy of magnesium.

Answer 7

Mg3+=Mg4+ + e-

Question 8

Why does ionisation energies decrease down groups?

Answer 8

-More shells

-More shielding

• Distance and shielding outweigh increase in nuclear charge, less attraction on outer most electron from nucleus

-So less energy needed to remove an electron