chemistry a level question about ionisation energies

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Mcressman12
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My textbook says there are three factors that affect ionisation energy: atomic radius, nuclear charge and electron shielding. Surely, atomic radius is a product of the factors nuclear charge and electron shielding, not a factor in itself? i am just getting confused as to how to awnser the exam questions and weather or not i need to mention it.
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fridacatlo
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Yes you do need to mention it. Atomic radius is essentially the distance between the outer electron and the nucleus, so is different to nuclear charge (the number of protons in the nucleus) and electron shielding (the effect of the inner electrons). When going down a group, eg group 7, the increase in nuclear charge is cancelled out by the increased number of inner electrons, so the outer electron of each group 7 element feels a net attraction of 7+. The ionisation energy decreases down the group though, so this can only be down to increased atomic radius. For questions like that, you would need to include it, as it's the defining factor
Hope that helps
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Mcressman12
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(Original post by fridacatlo)
Yes you do need to mention it. Atomic radius is essentially the distance between the outer electron and the nucleus, so is different to nuclear charge (the number of protons in the nucleus) and electron shielding (the effect of the inner electrons). When going down a group, eg group 7, the increase in nuclear charge is cancelled out by the increased number of inner electrons, so the outer electron of each group 7 element feels a net attraction of 7+. The ionisation energy decreases down the group though, so this can only be down to increased atomic radius. For questions like that, you would need to include it, as it's the defining factor
Hope that helps
So just to summarise for my sake: electron shielding refers to the blocking of valence shell electron attraction by the nucleus due to the presence of inner-shell electrons. So this means that going down the group the net nuclear charge relative to the valance electrons is the same, e.g. 7+ for group 7 elements. Thus the decreased nuclear attraction to valance electrons down the group must be caused by the increase in atomic radius which is due to the valance electrons being on a new shell further away from the nucleus. So saying that Xe has more shells than Ne is like saying that Xe has a larger atomic radius than Ne. That makes sense now as to why atomic radius should be a factor, thank you. But now I have another question, we are old we can say that shielding "outweighs" increased nuclear charge down the group, wouldn't it be better to say shielding "balances" the increased nuclear charge down the group?
Last edited by Mcressman12; 4 weeks ago
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