Sigma Bond
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#1
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#1
Hi,

wondering if anyone can help me with these questions,

"From the first 18 elements only, choose an element which fits the following descriptions,

The element which has the smallest third ionisation energy

The element with the first six successive ionisation energies shown below,

738, 1451, 7733, 10541, 13629, 17995"

If anyone could explain to me what the answers are then it would be greatly appreciated.
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EierVonSatan
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#2
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When you look at ionisation energies, you're mainly looking for large gaps - this gives you a good idea as to which group they are in, in the periodic table.

So for the element with the smallest 3rd ionisation energy, we're looking for an element that is easy to remove the first, second and third electrons but hard to remove the fourth. Recall that moving from left to right along a period, electronegativity also increases.
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Sigma Bond
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#3
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(Original post by EierVonSatan)
When you look at ionisation energies, you're mainly looking for large gaps - this gives you a good idea as to which group they are in, in the periodic table.

So for the element with the smallest 3rd ionisation energy, we're looking for an element that is easy to remove the first, second and third electrons but hard to remove the fourth. Recall that moving from left to right along a period, electronegativity also increases.
Thanks, I think the element is Mg, for the six ionisation energies question. However I still can't figure out the smallest third ionisation one. I'm probably over-complicating it.
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Kallisto
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#4
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#4
(Original post by Sigma Bond)
Hi,

wondering if anyone can help me with these questions,

"From the first 18 elements only, choose an element which fits the following descriptions,

The element which has the smallest third ionisation energy (...)
In KJ/mol? The smallest third ionisation energy of the first 18 elements which I have found out is 2744,80 KJ/mol. This third ionisation energy belongs to aluminium.
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Sigma Bond
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#5
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(Original post by Kallisto)
In KJ/mol? The smallest third ionisation energy of the first 18 elements which I have found out is 2744,80 KJ/mol. This third ionisation energy belongs to aluminium.
How would you work this out by looking at the periodic table?
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Kallisto
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#6
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(Original post by Sigma Bond)
How would you work this out by looking at the periodic table?
To be honest, I have no idea. It is possible to determine the ionisation energy in general by the number of electron shells and protons. The periodic table contains both. But it is completely different by another ionisation energies. Some atoms have just the first ionisation energy, some of them the second one. And that may go on till the seventh one. I don't know how to find the regularity out by periodic table. Sorry!
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mitchellshazia
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#7
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Ionisation energy decreases with increasing number of shells, because of increasing distance from the nucleus and electron shielding. So for the smallest third ionisation energy, we want something with the greatest number of shells - so something from period 3 since you are choosing from the first 18. Sodium and magnesium have fewer than three electrons in their outer shells, so when removing a third, you are taking it from the second shell, not the third - so something from aluminium to argon. Ionisation energy increases across a period, so the smallest must be aluminium.
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Sigma Bond
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#8
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(Original post by Kallisto)
To be honest, I have no idea. It is possible to determine the ionisation energy in general by the number of electron shells and protons. The periodic table contains both. But it is completely different by another ionisation energies. Some atoms have just the first ionisation energy, some of them the second one. And that may go on till the seventh one. I don't know how to find the regularity out by periodic table. Sorry!
Thanks for the help anyway!
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Pigster
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#9
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#9
Al has the smallest 3rd IE value.

Mg has the stated IE values.
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