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urgent alevel chemistry question help please (ionisation energies)

hi guys! I have a test tmr and I was doing some extra revision by going over some past questions.
I don't understand this question here (I'll try and attach it)

Screenshot 2022-10-06 at 11.09.35.png

the answer is aluminium but I am unsure as to how they got that as the answer.

I thought that because there is a massive energy change between group 1 and group 2, it would mean that the element is in group 1, but clearly not.
thank you for the help :smile:
(edited 1 year ago)
Original post by harlz_chalamet
hi guys! I have a test tmr and I was doing some extra revision by going over some past questions.
I don't understand this question here (I'll try and attach it)

Screenshot 2022-10-06 at 11.09.35.png

the answer is aluminium but I am unsure as to how they got that as the answer.

I thought that because there is a massive energy change between group 1 and group 2, it would mean that the element is in group 1, but clearly not.
thank you for the help :smile:




The significant jump in ionisation energies is between the 3rd and 4th ionisation energy. Corresponding to a change in energy level (orbital) at the 4th electron being removed. Therefore the element will have 3 electrons in its outer shell.

So you find the element in group 3. Aluminium. Which as an electron configuration of 2,8,3. You can see from the configuration that it supports the pattern of ionisation energies.
Original post by KMaisey
The significant jump in ionisation energies is between the 3rd and 4th ionisation energy. Corresponding to a change in energy level (orbital) at the 4th electron being removed. Therefore the element will have 3 electrons in its outer shell.

So you find the element in group 3. Aluminium. Which as an electron configuration of 2,8,3. You can see from the configuration that it supports the pattern of ionisation energies.


hi!! I understand more thank you!

out of interest, how can you see the electron configuration from the pattern of ionisation energies ???
Original post by harlz_chalamet
hi!! I understand more thank you!

out of interest, how can you see the electron configuration from the pattern of ionisation energies ???

So because you can see from the ionisation energies that the biggest jump is between the 3rd and 4th ionisation, you can deduce that the number of electrons in the outer shell must be 3. Because trying to remove electron number 4 requires a lot more energy as it is in the next shell, closer to the nucleus. So it had to be an element in group 3. Therefore the electron configuration had to end with a 3.

Looking at the question it states that the element is in period 3, so you look along the period 3 to read which element is in group 3. Which was aluminium.

I worked out the electron configuration by looking at how many electrons it had, although in this question the only bit you needed to work out was the number of electrons in the outer shell.

Below I have included a link to a very useful website, where it has all of the Chemistry A-level content you could need. I used it religiously for my A-level. The page I have linked explains how to find the group of an element using ionisation energies.


https://www.chemguide.co.uk/atoms/properties/moreies.html

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