ionization energies and group numbers. what is ionization? consider an atom of lithium, losing its...
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Ionization Energies and Group Numbers
What is Ionization?
• Consider an atom of Lithium, losing its electrons
• The lithium atom has three electrons (1s22s1) and three protons
+
• It is electrically neutral• 3 e- + 3p+ = Li0
What is Ionization?
• When Lithium loses an electron, it becomes positively charged
• 2 e- + 3p+ = Li+ +
• Li0 Li1+
Ionization Energy
• This is fairly easy to do. It takes little energy
• It has only 3 protons pulling the electron in.
• It is relatively far away from the nucleus
• It is being “shielded” by two other electrons.
++++{
Ionization of Multiple Electrons
• Consider how difficult it would be to ionize the 2nd electron
• It will be much more difficult and require more energy to remove this electron
+
• Li1+ Li2+
Ionization of Multiple Electrons• It still has 3 protons
pulling the electron in.• It is much closer to
the nucleus and so has a stronger pull
• It is not being “shielded” by other electrons.
++++{
Ionization of Multiple Electrons
• The 3rd electron would be just a little more difficult than the 2nd electron
+
• Li2+ Li3+
Ionization of Multiple Electrons
0 1rst 2nd 3rd
Electron Number
IE(kJ/mol)
• 1rst electron is not hard
• 2nd electron is much harder
• 3rd electron is little different
A graph of the ionization energy of Lithium vs. electron number would look like:
Ionization of Multiple Electrons
The large “jump” in energy needed between removing the 1st and 2nd electrons comes from the change in levels of the electrons.
0 1rst 2nd 3rd
Electron Number
IE(kJ/mol)
Ionization of Multiple Electrons
• These graphs can reveal which electrons are easy to remove and which are hard
• Read carefully, they, can also reveal the details of the electron structure. 0 1rst 2nd 3rd
Electron Number
IE(kJ/mol)
Easy
Hard
2s1
1s2 1s1
Ionisation energies and group numbersSuccessive ionization energies for potassium
Potassium is in group 1
Notice the “jump” in energy needed to remove the 2nd electron
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
0 2 4 6 8 10 12 14 16 18 20
electron removed
log10 of ionisation
energy
Ionisation energies and group numbersSuccessive ionisation energies for potassium
The different “jumps” are evidence for the arrangement of electrons in energy levels and sub-levels
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
0 2 4 6 8 10 12 14 16 18 20
electron removed
log10 of ionisation
energy
level 1(2 electrons)
level 2 (8 electrons)
level 3 (8 electrons)
level 4 (1 electron)
Which group is this element in?
Group 4
Notice the “jump” in energy needed to remove the 5th electron
0
5000
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15000
20000
25000
30000
35000
40000
45000
50000
0 1 2 3 4 5 6 7
electron removed
kJ/mol
Ionisation energies and group numbers
Which group is this element in?
Group 2
Notice the “jump” in energy needed to remove the 3rd electron
0
2000
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6000
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10000
12000
14000
16000
18000
20000
0 1 2 3 4 5 6 7
electron removed
kJ/mol
Ionisation energies and group numbers
Which group is this element in?
Group 3
Notice the “jump” in energy needed to remove the 4th electron
0
2000
4000
6000
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10000
12000
14000
16000
18000
20000
0 1 2 3 4 5 6 7
electron removed
kJ/mol
Ionisation energies and group numbers
Which group is this element in?
Group 5
Notice the “jump” in energy needed to remove the 6th electron
0
2000
4000
6000
8000
10000
12000
14000
0 1 2 3 4 5 6 7
electron removed
kJ/mol
Ionisation energies and group numbers
Which group is this element in?
Group 1
Notice the “jump” in energy needed to remove the 2nd electron
0
2000
4000
6000
8000
10000
12000
0 1 2 3 4 5 6 7
electron removed
kJ/mol
Ionisation energies and group numbers
Credits
• With the inspiration and original work of Nigel Saunders, Creative Chemistry