I'm having some trouble understanding how coloured solutions like copper(II) sulfate can remain blue.

All started in my chemistry class, in the transition elements lesson. The teacher said that the 3d orbital of copper gets split into two: 3d_xy, 3d_yz, 3d_xz and 3d_x^2-y^2, 3d_z^2 when it is ionised and hydrated (like in CuSO4). Then, one electron from the first triplet of orbital will go up into the second doublet of orbital when it absorbs energy, in the form of light. This process absorbs violet and red wavelengths of light and reflects blue. Then, the ion is stable and the electron remains up there, in the second doublet orbital.

But I was wondering, how can the solution of copper sulfate remain blue, if there are no more electrons moving from one energy level to another? :confused:I asked my teacher, but she said the electrons do not change orbital, and the solution remains blue. =/

That just didn't make sense to me. I tried consulting my physics teacher, and he told me that indeed, the electron is affected by light, and resonance occurs in the orbital, so that the electron changes orbitals constantly, up and down.

But to be sure, I decided to ask here, if anyone can confirm it?

Thanks!

Stay with your physics teacher! Here is the clue within your explanation: "Then, one electron from the first triplet of orbital will go up into the second doublet of orbital when it absorbs energy, in the form of light." It absorbs the energy of the light ("goes up"), then it spontaneously goes back to the original, lower energy level, a more stable state. And then "goes up" again. Hydrated Cu2+ ions absorb yellowish-orange light. The blue color is not what they "reflect", blue color is white light minus "yellowish-orange" wavelengths, exclusively picked out by hydrated Cu2+.

Ok, but that also means that the Cu^2+ is also emitting light, since one electron goes from a higher orbital to a lower one... :confused:

Not all transitions from higher to lower energy levels cause emission! You can't count on light emission in every transition, because there are multiple other ways to dissipate the energy difference.

Hmm... such as? I can't picture any way right now of how the electron gets to a lower energy level, without the 'lost' energy being emitted :(

It took people decades of experimenting to "picture" this stuff. This is sometimes called "radiationless transition".

Ok, I think I'll look for that. Thanks for your help! :)