Why do the colours of the halogens change from Fluorine to Iodine?

[tempo]

hey,

 

why do the colours of the halogens change from Fluorine to Iodine?

[ecoli]

I didn't know fluorine and iodine were colors!

[Daecon]

My guess is the number of electrons orbiting the nucleus, or the mass of the atoms themselves make them absorb/reflect different wavelengths of the light spectrum.

 

They're not the same atom, so there's no real reason to expect them to absorb/reflect the same colour light.

[Kermit]

Atoms of elements give off light when the electrons go from the excited state to the ground state.

Also, every element has its own spectrum unique to it.

[akcapr]

not in this case. thats only in a reaction, etc.

[jdurg]

not in this case. thats only in a reaction, etc.

 

Not sure what you mean there, but each element absolutely DOES have a unique spectrum and they do NOT have to be involved in a reaction for that spectrum to exist.

 

In regards to the colors of the halogens, it probably does have something to do with the arrangement of the electrons as each of the halogens does have a color to it and that's a unique trait amongst that group. Since the noble gases right after the halogens are colorless, it would make one think that the one electron short of a full shell plays a part in how the halogens absorb/reflect light.

[tempo]

In regards to the colors of the halogens, it probably does have something to do with the arrangement of the electrons as each of the halogens does have a color to it and that's a unique trait amongst that group. Since the noble gases right after the halogens are colorless, it would make one think that the one electron short of a full shell plays a part in how the halogens absorb/reflect light.

 

yeh that makes sense ^

 

would you also know why the halogens get darker as u go down the group?

 

as the shells further out are being filled, and the energy jump between the further shells is smaller, i would have thought that the halogens would go from violet to red as u go down the group, as the electrons would only need a small amount of energy (hence related to red as opposed to violet) to move to a higher energy level before releasing this energy again.

[jdurg]

When we see the color of a liquid, solid, or gas, it's due to light being scattered by that object. The sky appears blue because of this light scattering, as do the halogens. Chlorine, for example, will scatter the green portion of the visible spectrum more than any other portion, so when you look at chlorine you see a greenish colored gas. Bromine will scatter the red-orange portion of the spectrum so you see the red-orange color better. Iodine is the same with violet.

 

When you look at the periodic table, you can kind of make sense of this. Fluorine and chlorine each have s and p orbitals filling up, so they're fairly similar in that regard. Fluorine is a very pale yellow color and chlorine is a pale green. If you go by the ROYGBIV arrangement of light energies, you'd see that flourine absorbs the lower energy waves a bit better and then scatters them around. Chlorine absorbs the higher energy waves better and then scatters those around. Still, both gases are pretty pale in their colors.

 

When you move down to Bromine and Iodine, you start putting in the d subshells and the colors of those halogens are MUCH more intense. Once again, the lower atomic number halogen has a weaker energy color (Orange) while the higher atomic number halogen has a stronger energy color (Violet). I'm sure there is some correlation between the electron shells and the reasoning behind the color. But when looking at the elements with the same kinds of shells (Fluorine/Chlorine, then Bromine/Iodine) you see that the lower atomic number scatters the lower energy color better.

 

Also remember that the color you see from a halogen is different in origin than the color you see from a metal salt in a flame. Halogens aren't emitting light like an excited metal salt does. A halogen is simply altering how the existing light gets to you. (If you have halogens in a dark room, you can't see their color. If you excite a metal ion in a dark room, you'll see the color as it is emitting its own light).

[tempo]

ah ok, i understand now.. thank you so much for writing that up.