Talk:Color of chemicals

Colour of chemicals......



From PNA/Chemicals

 * Colors of chemicals is written in schoolteacher form, has some format problems, and also has some factual errors as brought up on its talk page. Needs help. --Alex S 04:51, 17 Mar 2004 (UTC)


 * Suggest move of relevant information to Color under the heading 'Chemistry of color' and keeping info on specific ion colors on this page. Needs discussion on its talk page.MGM 19:30, Apr 19, 2004 (UTC)


 * I agree to MGM but then the Titel of the article should be changed accordingly.FriedrichB 02:53, 3 November 2006 (UTC)

Colors of common chemical compounds

hydrated ions
name   formula    colour
 * alkali metals  M^+  none
 * alkaline earth metals  M^2+  none
 * scandium Sc^3+  none
 * titanyl  TiO^2+    none
 * vanadate VO4^3-  none
 * vanadyl VO^2+    yellow
 * chromium(III) Cr^3+  green
 * chromate   CrO4^2- yellow
 * dichromate Cr2O7^2-  orange

(to be continued)

Hydrated Salts
Some distinction should be made between the fact that most salts are colorless when anhydrous, and only take on color when H2O is introduced into the crystalline structure. I'm a little sketchy on the chemical reasons behind this, though, so someone with a bit more experience than I should work on it. Also, the salts table probably ought to be expanded - I can work on that. K1avg 15:33, 30 Apr 2005 (UTC)

Organic compounds
Shouldn't there be alot of organics here, too? I'll see if I can find a representitive list... Adqam 14:14, 16 December 2005 (UTC)

As far as I know, not many common organic compounds have vivid colors; color is rarely used to distinguish between organic compounds. --Thezookeeper 22:57, 28 December 2005 (UTC)


 * Off the top of my head there's lycopene, which is responsable for the red colouring of tomatoes. I agree that there are not many; but would argue that the organics that are coloured are somewhat significant. Adqam 16:47, 4 January 2006 (UTC)

Other
What exactly do you mean by giving colors for potassium, sodium, and hydrogen gas? Potassium gives off a purple flame when BURNED and sodium gives off a yellow flame when BURNED, but the elements are not purple or yellow by any means. And hydrogen gas is pretty...colorless... --Thezookeeper 03:55, 12 December 2005 (UTC)


 * There is already an article about flame coloration i.e. Flame_test. Therefore this one should concentrate on the dissolved ions shouldn't it? --KIce 12:44, 22 January 2006 (UTC)
 * Yeah 43.229.90.225 (talk) 08:56, 11 March 2022 (UTC)

Quantum mechanics
There are complications: cobalt chloride is pink or blue depending on the state of hydration (blue dry, pink with water) so it's used as a moisture indicator in silica gel... Zinc Oxide is white, but IIRC, at higher temperatures becomes yellow, returning to white as it cools, and Strictly speaking, the cuprammonium ion isn't a hydrated ion.. Malcolm Farmer 20:31, 31 Jul 2003 (UTC)

What is all this talk of electron clouds being big or small ? It doesn't make any sense to me :-( As far as I ever knew colour is caused by the difference in energy of atomic or  molecular orbitals being in the region of visible light. Alkaline metals have white compounds because the energy levels are widely spaced and therfore correspond to UV. Transition metals have coloured compunds because the d orbital of the (N-1)th shell and the s orbital of the of the Nth shell are much closer together in energy and are therfore able to absorb visible light.Have I been taught wrong ? theresa knott 13:50, 2 Dec 2003 (UTC)

theresa, your comments sound detailed enough to have merit; it's a good question. the article leaves you inferring there must be some correlation between the wavelength (or half?) and the cloud radius/diameter, though not necessarily discrete. are we talking reflective effect, absorption/reemission, etc. kind of the heart of the issue, would be interesting to see it detailed. Chris Rodgers 07:34, 8 Apr 2004 (UTC)


 * You're right that the color of a substance depends on the spacing of its orbitals. I have an incomplete sort of idea about how this is related to the size of the electron clouds.


 * Why do we have orbitals in the first place? Why are electron energy levels quantized?  They're quantized because they're confined to a very small space.  The more you confine them, the broader the gaps between possible energy levels.  The addition of an atom to a molecule increases the available space and reduces the confinement. --Smack (talk) 19:57, 11 Jan 2005 (UTC)


 * That's not true at all. The energy gap between levels has nothing whatsoever to do with the size of the orbitals.  In the case of the transition metal complexes that seem to be the focus of this particular article, the  relevant energy gap is called the "Ligand Field Splitting Parameter."  This parameter is a characteristic of the metal ion and the ligand(s) present.  See the article Ligand Field Theory. Ulthar 19:36, 17 April 2007 (UTC)

I see if I can help you guys out. Since I study chemistry. It's a subject I feel I can contribute to. --MGM 15:22, Apr 18, 2004 (UTC)

Am I getting anything wrong?
Or is the introduction really as stupid as it sounds to me?

SundarKanna 08:34, 26 December 2005 (UTC)

Redo Intro
I'm hoping someone will support my drastic edit. The intro was unfocused, not clear, and in some cases wrong. Other pages are already devoted to color, light, quantum theory, spectroscopy, etc. This page, if it deserves to exist at all, should be clear about the connection between chemicals and colors, and give a clear explanation of why they have the colors they do. I tried to do that with this intro. I'm not going to remove the cleanup tag, but hopefully if this is a good edit someone will. Also a more concise title might be in order, if anyone has any ideas? -Id711 22:43, 11 July 2007 (UTC)


 * From the point of view of someone almost entirely ignorant about this subject, here are my comments on the intro:

"All chemical compounds, including atoms, are capable of absorbing and releasing energy. The amount(s) of energy (quanta) absorbed and released is determined by the quantum structure of the chemical. The release of energy visible to the human eye spans the wavelengths 380 nm to 760 nm and is commonly referred to as color."


 * This paragraph, and the article in general, seems to be crying out for the mention of the words "electromagnetic radiation".

"The relationship between energy and wavelength is determined by the equation:
 * $$E = hf = \frac{hc}{\lambda} \,\! $$

where E is the energy of the quanta (photon), h is Planck's constant(=6.62606957(29)×10−34), $$\lambda$$ is the wavelength and c is the speed of light."


 * The relevance of this to colour is not terribly clear.

"The relationship between chemical structure and energy can be understood using atomic orbital, molecular orbital, or Ligand Field Theory."


 * Is this sentence grammatically correct? Or does it mean "atomic orbital theory, molecular orbital theory, or Ligand Field Theory"?

"In organic compounds the color can be determined by the difference between the Highest Occupied Molecular Orbital and the Lowest Unoccupied Molecular Orbital. The energy absorbed and/or released does not directly correlate to what humans perceive as color."


 * 1. I find this last sentence confusing. To me it suggests that there is some other entirely different factor that influences colour. I'm guessing what's trying to be said is that the relationship between absorption/emission and colour is fairly complex, but that doesn't really come across.


 * 2. In that light, it might be better in the first sentence to say "the absorption/emission profile can be determined", or similar, rather than "the color can be determined".


 * 3. The conjunction of these two sentences suggests that the second sentence only applies to organic compounds, which I assume is not the case.

Matt 19:54, 2 August 2007 (UTC).

Recommend for deletion
This article is so full of misinformation and so utterly lacks a unifying theme that it arguably does more harm than good to non-expert readers. I can absolutely see the benefit of an article that surveys the many origins of color in chemical systems, but this article is not it. Even the title, "color of chemicals," makes me cringe, and furthermore, is not relevant to most of the things in the article itself. Ions are not chemicals. Flames are not chemicals. I applaud the work of some editors to improve what was an even worse article a few years ago, but nevertheless, it remains a strong recommendation for deletion. -75.150.254.105 (talk) 22:03, 1 October 2012 (UTC)

What about anions
Such as I- which is usually colorless. — Preceding unsigned comment added by 172.248.197.0 (talk) 19:12, 13 September 2015 (UTC)