Ionisation Energy: Trends & Evidence

Question 1

The second ionisation energy (IE2) is the

Answer 1

The second ionisation energy (IE2) is the energy required to remove the second mole of electrons from each +1 ion in a mole of gaseous +1 ions, to form one mole of +2 ions

Question 2

The third ionisation energy (IE3) is the

Answer 2

energy required to remove the third mole of electrons from each +2 ion in a mole of gaseous +2 ions, to form one mole of +3 ions

Question 3

: Equations representing ionisation energies must have ………….. (…) state symbols for the atoms and ions but not for the electrons.

Answer 3

gaseous (g)

Question 4

Why does the successive ionisation energy go up as you remove more electrons

Answer 4

This is because once you have removed the outer electron from an atom, you have formed a positive ion
Removing an electron from a positive ion is more difficult than from a neutral atom

As more electrons are removed, the attractive forces increase due to decreasing shielding and an increase in the proton to electron ratio

The increase in ionisation energy, however, is not constant and is dependent on the atom’s electronic configuration

Question 5

Calcium example

Answer 5

The first electron removed has a low IE1 as it is easily removed from the atom due to the spin-pair repulsion of the electrons in the 4s orbital

The second electron is more difficult to remove than the first electron as there is no spin-pair repulsion

The third electron is much more difficult to remove than the second one corresponding to the fact that the third electron is in a principal quantum shell which is closer to the nucleus (3p)

Removal of the fourth electron is more difficult as the orbital is no longer full, and there is less spin-pair repulsion

The graph shows there is a large increase in successive ionisation energy as the electrons are being removed from an increasingly positive ion

The big jumps on the graph show the change of shell and the small jumps are the change of subshell

Question 6

Successive ionisation data can be used to

Answer 6

Predict or confirm the simple electronic configuration of elements

Confirm the number of electrons in the outer shell of an element

Deduce the Group an element belongs to in the Periodic Table

Question 7

By analysing where the large jumps appear and the number of electrons removed when these large jumps occur, the

Answer 7

he electron configuration of an atom can be determined