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Chemistry - Group 2 Flame Tests

Each corresponding flame colour is due to the excited electrons falling back to their ground state and releasing a form of energy - namely visible light. Now, according to many websites the higher the energy gap (which increases down Group 2) the higher the frequency of visible light. For e.g starting with Calcium and ending with Barium - the flame colours truly do increase in colour frequency - with Brick-red, Crimson, and Apple-green colours respectively.

What I don't understand - if the energy gaps increase down the Group and therefore the frequency of energy along the EM spectrum increases too, why do Magnesium and Berylium (which should have the lowest energy gaps) have the highest frequencies along the EM spectrum - i.e. emitting UV light?

Reply 1

Squishy•

What board is this for and is it AS or A2?

Reply 2

Ahh I see, you're amazing I swear- so technically it doesn't matter how many energy levels an element originally has? - if the electrons are tightly bound to the nucleus - it can always move to very high energy levels due to their excited state, whereas if an element isn't so close to the nucleus it can already move to high energy levels because extra shells mean higher energy levels. I'm guessing this works on a two way basis - like you need a balance between a very close nucleus and high energy levels.

(edited 8 years ago)

Reply 3

Original post by Squishy•

What board is this for and is it AS or A2?

Lol it's AS but sometimes I need to learn beyond my level to understand the concept a bit more. :wink:

Reply 4

Squishy•

Original post by I <3 WORK

Lol it's AS but sometimes I need to learn beyond my level to understand the concept a bit more. :wink:

oh right i never learnt flame tests in AS

Reply 5

Original post by Squishy•

oh right i never learnt flame tests in AS

Which exam board do you do? :smile:

Reply 6

Squishy•

Original post by I <3 WORK

Which exam board do you do? :smile:

AQA

Reply 7

Original post by Squishy•

AQA

Ahh I see - well I do Edexcel so I guess that's what makes the difference.

Reply 8

Squishy•

Original post by I <3 WORK

Ahh I see - well I do Edexcel so I guess that's what makes the difference.

Oh alright then I love you sweet dreams

Reply 9

No way your explanations are amazing! May I ask, are you some sort of Chemistry/Physics professor by any chance? :top2:

On a serious note, this stuff makes so much more sense so thank you! :u:

Forgive me for asking a million more questions - but can we safely say that the best conditions for an element to give off energy with the highest frequency (when returning to the ground state from an excited state) should be: Having the element's electrons being close to the nucleus AND having a large difference in energy between energy levels. (E.g. Beryllium/Magnesium)

Whereas the conditions to have a fairly high frequency (though not as high as the condition above) could be the case where an element would have a much lower energy difference between energy levels, yet because the electrons have already filled higher energy shells the resultant frequency of the photons released would be high. (E.g. Strontium/Barium)