MODULE 2
7
WORKSHEET
IONISATION ENERGY
Syllabus reference 8.3.2
1
Define ionisation energy.
Ionisation energy is the energy required to remove an electron from the outer-most energy level of
a gaseous atom.
2
Consider the following information on ionisation energies.
PERIOD
SYMBOL
ATOMIC NUMBER
GROUP
IONISATION
ENERGY (kJ/mol)
2
Li
3
1
519
Be
4
2
900
B
5
3
799
C
6
4
1090
N
7
5
1400
O
8
6
1310
F
9
7
1680
Ne
10
8
2080
Na
11
1
494
Mg
12
2
736
Al
13
3
577
Si
14
4
786
P
15
5
1060
S
16
6
1000
Cl
17
7
1260
Ar
18
8
1520
3
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CONQUERINGCHEMISTRY PRELIM
MODULE 2 WS 7
a
Use the data in the table above to plot, on the same axes, a graph of ionisation energy versus
group number for each of Periods 2 and 3.
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Use the graphs from part a to describe the trend in ionisation energy as you move from left to
right along a period.
In moving from left to right across the Periodic Table first ionisation energy generally increases.
c
Compare the ionisation energies of Li and Na, C and Si, and F and Cl. What does this suggest
regarding trends from top to bottom?
Moving from top to bottom of the Periodic Table first ionisation energy decreases.
Copyright © 2008 McGraw-Hill Australia
CONQUERINGCHEMISTRY PRELIM
MODULE 2 WS 7
3
Using the graph in question 2a and the metal activity series from your textbook, circle (on the
graph) the two most active metals and put squares around the next most active metals.
a What relationship is there between activity and ionisation energy?
The lower the ionisation energy the more active the metal.
b
Does the data below support or refute the generalisation you made in part a? Why?
SYMBOL
ATOMIC NUMBER
IONISATION ENERGY (kJ/mol)
Ca
20
596
Fe
26
766
Au
79
891
Yes. Ca is more active than Fe which is more active than Au and the order from lowest to
highest ionisaton energy is also Ca, Fe, Au.
4
Scientists discovered a new metal X with an ionisation energy of 650 kJ/mol. Using the data in the
questions above, where in the activity series could this metal be placed? Explain your reasoning.
On the basis of ionisation energy this metal would be placed between Mg and Al because the
ionisation energy of Mg is 736 and that of Al is 577.
Copyright © 2008 McGraw-Hill Australia
CONQUERINGCHEMISTRY PRELIM
MODULE 2 WS 7