Ionization Energy

Сентябрь 9, 2022

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Ionization Energy

Содержание

2. Ionization Energy The amount of energy required to completely remove an electron from a gaseous atom.
3. Ionization Energy The second and third ionization energies can be represented as follows: X+ (g) +
4. Group trends Ionization energy decreases down the group.
5. Going from Be to Mg, IE decreases because: Mg outer electron is in the 3s sub-shell
6. Notice any trends? Any surprises?
7. General trend: Increasing I.E. as we go across a period Look at the peak at Mg
8. Why is there a fall from Mg to Al? Al has configuration 1s2 2s2 2p6 3s2
9. Why is there a fall from P to S? This can be explained in terms of
10. Driving Force Full Energy Levels are very low energy. Noble Gases have full energy levels. Atoms
11. 2nd Ionization Energy For elements that reach a filled or half filled sublevel by removing 2
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Слайд 2

Ionization Energy
The amount of energy required to completely remove an electron

from a gaseous atom.
An atom's 'desire' to grab another atom's electrons.
Removing one electron makes a +1 ion.
The energy required is called the first ionization energy.
X(g) + energy →X+ + e-

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Ionization Energy
The second and third ionization energies can be represented as

follows:
X+ (g) + energy? X2+ (g) + e-
X2+ (g) + energy? X3+ (g) + e-
More energy required to remove 2nd electron, and still more energy required to remove 3rd electron

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Group trends
Ionization energy decreases down the group.

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Going from Be to Mg, IE decreases because:
Mg outer electron is

in the 3s sub-shell rather than the 2s. This is higher in energy
The 3s electron is further from the nucleus and shielded by the inner electrons
So the 3s electron is more easily removed
A similar decrease occurs in every group in the periodic table.

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Notice any trends? Any surprises?

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General trend: Increasing I.E. as we go across a period
Look at

the peak at Mg and the plateau between P and S. Can you explain why?

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Why is there a fall from Mg to Al?
Al has configuration

1s2 2s2 2p6 3s2 3p1, its outer electron is in a p sublevel
Mg has electronic configuration 1s22s22p63s2.
The p level is higher in energy and with Mg the s sub level is full – this gives it a slight stability advantage

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Why is there a fall from P to S?
This can

be explained in terms of electron pairing.
As the p sublevel fills up, electrons fill up the vacant sub levels and are unpaired.
This configuration is more energetically stable than S as all the electrons are unpaired. It requires more energy to pair up the electrons in S so it has a lower Ionisation energy.
There is some repulsion between the paired electrons which lessens their attraction to the nucleus.
It becomes easier to remove!

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Driving Force
Full Energy Levels are very low energy.
Noble Gases have full

energy levels.
Atoms behave in ways to achieve noble gas configuration.

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2nd Ionization Energy
For elements that reach a filled or half filled

sublevel by removing 2 electrons 2nd IE is lower than expected.
Makes it easier to achieve a full outer shell
True for s2
Alkaline earth metals form +2 ions.