Chemistry A-level exam q help!

username6119504

How to answer:
Element B has ionisation energy : 1500, 2700, 4000, 5800, 7200, 8800, 12000
•estimate 8th ionisation energy of element B and explain steps
Is there a really easy way to estimate ionisation energy that i havent noticed!

Reply 1

username6119504

OP

9

My snapchat AI said it was between 14000-15000 (i answered 14000) but i cant find the actual markscheme. If someone can still explain :smile:

I assumed the element B was group 6, total'd the previous ionisations and then from reasoning just answered it as 14k.

(edited 12 months ago)

Reply 2

jjeeeeeea

12

Is this the only information the question gave? If you look up the ionisation energies of argon, they are here:
1520.6, 2665.8, 3931, 5771, 7238, 8781, 11995, 13842, 40760, 46186 kJ/mol

So the element must be Argon, the thing is that given the information you have I think it could be either a group 7 or group 8 element (no big increase in IE yet).

If it was group 7, the 8th ionisation would come from a lower energy shell (closer to nucleus) so there would be a really big increase in IE (like when you go to 9th one in the IEs of Argon I showed)

If it was group 8, it is safe to say the trend in numbers will continue giving around a number of 14000.

I think the only way to do this is by inference, but it seems unusual they don't give you the group of the element in the question? I've seen similar questions which tell you the group

Reply 3

username6119504

OP

9

Original post by jjeeeeeea

Is this the only information the question gave? If you look up the ionisation energies of argon, they are here:
1520.6, 2665.8, 3931, 5771, 7238, 8781, 11995, 13842, 40760, 46186 kJ/mol

So the element must be Argon, the thing is that given the information you have I think it could be either a group 7 or group 8 element (no big increase in IE yet).

If it was group 7, the 8th ionisation would come from a lower energy shell (closer to nucleus) so there would be a really big increase in IE (like when you go to 9th one in the IEs of Argon I showed)

If it was group 8, it is safe to say the trend in numbers will continue giving around a number of 14000.

I think the only way to do this is by inference, but it seems unusual they don't give you the group of the element in the question? I've seen similar questions which tell you the group

I attached the question. It’s “consecutive” in atomic number which I forgot to even factor in😭

(edited 12 months ago)

OP

Original post by jjeeeeeea

Is this the only information the question gave? If you look up the ionisation energies of argon, they are here:
1520.6, 2665.8, 3931, 5771, 7238, 8781, 11995, 13842, 40760, 46186 kJ/mol

So the element must be Argon, the thing is that given the information you have I think it could be either a group 7 or group 8 element (no big increase in IE yet).

If it was group 7, the 8th ionisation would come from a lower energy shell (closer to nucleus) so there would be a really big increase in IE (like when you go to 9th one in the IEs of Argon I showed)

If it was group 8, it is safe to say the trend in numbers will continue giving around a number of 14000.

I think the only way to do this is by inference, but it seems unusual they don't give you the group of the element in the question? I've seen similar questions which tell you the group

how come it wont be group 6? I thought the jump between 6th and 7th showed that the 7th electron was removed from a lower sub-shell?

Reply 5

jjeeeeeea

12

Original post by MirioTogata

I attached the question. It’s “consecutive” in atomic number which I forgot to even factor in😭

Ahh okay. You can tell from this information that B is in group 8.
Since C has a "jump" in IE from 1st to second, you can tell that it will have one outer electron.
As there are no jumps in IE in both A and B, it must be that they are either group 7 or 8, but since they are consecutive the sequence will go like this:
C: 1 outer electron
B: 8 outer electrons
A: 7 outer electrons

Since we now know element B is in group 8, you can use the logic from before

Reply 6

jjeeeeeea

12

Original post by MirioTogata

how come it wont be group 6? I thought the jump between 6th and 7th showed that the 7th electron was removed from a lower sub-shell?

The jump there isn't big enough to be caused by a whole different shell. Whenever they ask these questions they tend to make it super obvious what is a big jump.
If you look at the IEs of argon it goes from 14k all the way to 40k. The slight jump might be caused by a sub-shell but not a whole shell/energy level, which is what you're looking for. Hope that helps :smile:

Reply 7

username6119504

OP

9

Original post by jjeeeeeea

The jump there isn't big enough to be caused by a whole different shell. Whenever they ask these questions they tend to make it super obvious what is a big jump.
If you look at the IEs of argon it goes from 14k all the way to 40k. The slight jump might be caused by a sub-shell but not a whole shell/energy level, which is what you're looking for. Hope that helps :smile: