# Electron Transitions after Absorption of Photon

• Chemistry
• jolly_math
In the second case, after absorption has occurred, you are looking at the transitions down to a lower energy state, and that means look at d) and e) ."...the correct answer is d) 4p to 1sANDe) 4d to 1sif we ARE just looking at transitions up to higher energy levels (just absorption).f

#### jolly_math

Homework Statement
The absorption of the highest frequency photon will cause which transition(s) in the hydrogen atom?
a) 2p to 3s
b) 2p to 4d
c) 2p to 4s
d) 4p to 1s
e) 4d to 1s
f) 3s to 6f
Relevant Equations
transitions
When a photon is absorbed, electrons move from a lower energy level to a higher energy level, so my answer is a, b, c, and f.

I don't understand why the solution is b, c, d, e. Can electrons in this case move from a higher to lower energy level?

Thank you.

• Nickjohny
When a photon is absorbed, electrons move from a lower energy level to a higher energy level, so my answer is a, b, c, and f.
Yes, but which is/are caused by absorption of the highest frequency photon?
I don't understand why the solution is b, c, d, e. Can electrons in this case move from a higher to lower energy level?
Who says that's the solution? Absorption of a photon increases the energy, so d and e are wrong.

• jolly_math
No idea what this question asks, perhaps my English fails. "The highest frequency photon" doesn't make any sense to me. Highest of what?

• DrClaude
I think it's a bit badly worded.
Is it asking which photon absorption results in the highest energy transition from a low energy state to a high energy state.
Or is it asking after the highest absorption, which transition from a high energy state to a low energy state will result after the absorption.

In the first case you are looking for low to higher energy orbital transitions and must only look at options a), b), c) and f) and chose the one which is the highest energy transition. Which is what I initially thought it was asking.
In the second case, after absorption has occurred, you are looking at the transitions down to a lower energy state, and that means look at d) and e) .

But the suggested correct answer does neither of these, it looks at both steps up (the adsorption) and drops down (emission after adsorption). So is it just looking for the highest energy gap between two orbitals?

I suspect the question was written quickly and the result is a bit of confusion.

If we ARE just ooking at transitions up to higher energy levels (just absoprtion).
The energy levels for hydrogen depend only on the principle quantum number (I admit I had to check that in case I was thinking of something else). And the higher the n levels are, the closer and closer the next level up is to the one below (no need to check that one of course!)
So the transitions from a low value n to a higher level are what we are looking for.
i.e.
a) 2p to 3s
b) 2p to 4d
c) 2p to 4s

And the biggest transition(s) will be 2p to 4d, AND 2p to 4s, if we ARE looking at transitions up to higher energy. n = 2 to n = 4 in both cases

If we are looking at the drop back down transition, OR the highest overall transition, we look at
d) 4p to 1s
e) 4d to 1s
And BOTH are the biggest transitions of the entire set. From n = 4 to n = 1
(note that n=2 to n = 5, or n = 2 to n = 6 are smaller than the above because the n = 1 to n = 2 gap is very large)

It is testing if you know that in hydrogen only the principle quantum number really matters and that the gap between successive levels gets smaller and smaller.
It's a badly worded question testing you on something sneaky that only applies to hydrogen.

And after writing this out and thinking about it, I believe the correct answer has to be
d) 4p to 1s
AND
e) 4d to 1s

• DeBangis21 and jolly_math
If we ARE just looking at transitions up to higher energy levels (just absoprtion).
The energy levels for hydrogen depend only on the principle quantum number (I admit I had to check that in case I was thinking of something else). And the higher the n levels are, the closer and closer the next level up is to the one below (no need to check that one of course!)
So the transitions from a low value n to a higher level are what we are looking for.
i.e.
a) 2p to 3s
b) 2p to 4d
c) 2p to 4s

And the biggest transition(s) will be 2p to 4d, AND 2p to 4s, if we ARE looking at transitions up to higher energy. n = 2 to n = 4 in both cases

Why would f) (3s to 6f) not be a possible transition from a low to high energy level? Thanks.

An editing error - I deleted some text and rewrote it. and that transition must have been deleted by accident from the bit you quoted. But it's there in the earlier text.

"In the first case you are looking for low to higher energy orbital transitions and must only look at options a), b), c) and f) and chose the one which is the highest energy transition. Which is what I initially thought it was asking."

And although it's a jump of three values for n, these upper levels are very close together in energy. So those with n=2 going to n=4 are still bigger jumps than 3s to 6f.

Prove reading longer posts like the above can result in small typos like that. Sorry about that.

• jolly_math
Don't forget to consider selection rules.

• jolly_math
It might also be useful to google "Rydberg formula"