Is the flame colour due to the metal ion or the anion present? Why? (1 Viewer)

[Nyo]

• perform first-hand investigations to carry out a range of tests, including flame tests, to identify the following ions: phosphate; sulfate; carbonate; chloride; barium; calcium; lead; copper; iron.

Hey guys ^^; I would appreciate it if someone could explain this question for me:

<!--[if !supportLists]-->[FONT=&quot] [/FONT]<!--[endif]-->Is the flame colour due to the metal ion or the anion present? Why?

I know that it is metal ions that are present. But why not anions?

And.. If possible could someone give me an additional identifying test for Pb2+?


Thanks in advance ^^

 

[minijumbuk]

Flame tests can only be used to test for cations.

Hmm, there is a table that shows the different colours of cations in flame. I guess the other ones can be tested by precipitation, or AAS.

 

[Nyo]

Flame tests can only be used to test for cations.

Hmm, there is a table that shows the different colours of cations in flame. I guess the other ones can be tested by precipitation, or AAS.

I see ^^; So we can use AAS to test Pb too? Thanks for the response

Btw I love your siganture! Made me laugh so much ^^
Boo Kira

L <3 FTW!

EVERYONE WATCH Death note: L, Change the World!

 

[Steth0scope]

Yea AAS is specific for each element ... also flame tests can be used for SOME anions.

 

[Steth0scope]

No, you definately can. It is one of the methods used to test toxicity levels of water samples from rivers containing lead and other heavy metals etc

 

[undalay]

Nobody actually answered the question.
Why doesn't heating anions have flames/colours?

Something to do with valence shell filled, thus no other electrons are able to reach an excited energy level? I have no idea, just speculating

 

[Nyo]

AH! Thank you so much everyone ^_^
I've gained a better understanding :3

 

[Undermyskin]

I'm not that convinced. Sodium is NOT a transition metal. Still it gives the intense yellow colour! And I think potassium gives faint purple.

 

[xiao1985]

It all depends on relative energy gaps of filled and unfilled orbitals. Most metals (incl. Na, K, Ca, Sr, Ba) have energy gaps of filled and unfilled orbitals correspond to the energy of a photon, that is in the visible EMR range.

Anions are usually not visible as the energy gap do not correspond to that of a visible photon.

Pb2+, if I recall correctly, gives a pale purple colour. But the lead vapour emitted, as I heard, can be quite detrimental to human health (or so I heard). Therefore Pb flame test is not done in school. That been said, they can still be detected with AAS.

Theroetically, you can use the same method on anions. But it was never (not in AAS that I know of) nor in flame (since their energy gap is not that of a visible range).

 

[Forbidden.]

It all depends on relative energy gaps of filled and unfilled orbitals. Most metals (incl. Na, K, Ca, Sr, Ba) have energy gaps of filled and unfilled orbitals correspond to the energy of a photon, that is in the visible EMR range.

Anions are usually not visible as the energy gap do not correspond to that of a visible photon.

Pb2+, if I recall correctly, gives a pale purple colour. But the lead vapour emitted, as I heard, can be quite detrimental to human health (or so I heard). Therefore Pb flame test is not done in school. That been said, they can still be detected with AAS.

Theroetically, you can use the same method on anions. But it was never (not in AAS that I know of) nor in flame (since their energy gap is not that of a visible range).

Yeah I wrote something like that as my HSC response last year that using a flame test on Pb was dangerous because it is a heavy and toxic metal.
+1 mark.