Why Is Gold Yellow?

[mn90403]

And ... Why does it not corrode easily?

 

It is all explained by Einstein's Theory Of Relativity.

 

https://www.livescience.com/58245-theory-of-relativity-in-real-life.html 

 

Most metals are shiny because the electrons in the atoms jump from different energy levels, or "orbitals." Some photons that hit the metal get absorbed and re-emitted, though at a longer wavelength. Most visible light, though, just gets reflected.

Gold is a heavy atom, so the inner electrons are moving fast enough that the relativistic mass increase is significant, as well as the length contraction. As a result, the electrons are spinning around the nucleus in shorter paths, with more momentum. Electrons in the inner orbitals carry energy that is closer to the energy of outer electrons, and the wavelengths that get absorbed and reflected are longer. [Sinister Sparkle Gallery: 13 Mysterious & Cursed Gemstones]

 

Longer wavelengths of light mean that some of the visible light that would usually just be reflected gets absorbed, and that light is in the blue end of the spectrum. White light is a mix of all the colors of the rainbow, but in gold's case, when light gets absorbed and re-emitted the wavelengths are usually longer. That means the mix of light waves we see tends to have less blue and violet in it. This makes gold appear yellowish in color since yellow, orange and red light is a longer wavelength than blue.

Gold doesn't corrode easily

 

The relativistic effect on gold's electrons is also one reason that the metal doesn't corrode or react with anything else easily.

 

Gold has only one electron in its outer shell, but it still is not as reactive as calcium or lithium. Instead, the electrons in gold, being "heavier" than they should be, are all held closer to the atomic nucleus. This means that the outermost electron isn't likely to be in a place where it can react with anything at all — it's just as likely to be among its fellow electrons that are close to the nucleus.

[Reg Wilson]

When gold is used for visors on space helmets it is so thin as to be transparent and is green in colour. It is used to screen out radiation.

[GotAU?]

Even though it’s very stable,  it is interesting how gold can still be dissolved by the chlorine in Agua Regia and becomes one molecule consisting of 1 gold atom and 4 chlorine atoms (AuCl4).

[PimentoUK]

When I was at school/college, this theory was used to suggest that ALL metals should be 'yellowish' , and the mystery was: why is nearly every metal in practice silver-coloured? Everything from light Lithium to heavy Lead seems uniformly silver/grey.

Gold is definitely shinier out into the infra-red range, hence why spacecraft tend to be smothered in gold foil. And in the engine-bay of the rather exotic McLaren F1 road car.

[Ridge Runner]

Guys this is like asking me why corn 🌽 always has a even row of corn on every cob . I don’t know why but it does.

 Now don’t you feel enlightened for you that didn’t know that ?

 Chuck 

[GB_Amateur]

1 hour ago, PimentoUK said:

When I was at school/college, this theory was used to suggest that ALL metals should be 'yellowish' , and the mystery was: why is nearly every metal in practice silver-coloured? Everything from light Lithium to heavy Lead seems uniformly silver/grey.

I agree with PimentoUK and call BS to the color thing explained in the original post's link.  Take a look at the periodic table, where next door neighbor elements have one less proton (if to the immediate left) or one more proton (if to the immediate right) proton in the nucleus and thus one less/more electron in the neutral atom.  One place to the left of gold is platinum and one to the right is mercury.  Both are the color white at room temperature.  And what about copper?  Its nucleus contains only 29 protons (compared to gold's 79) yet it is yellowish in color, too.

Francium has 8 more protons in its nucleus than gold as well as a single electron in its outermost shells.  It's considered the most extremely reactive element found in nature with a single outer shell electron and is a member of the alkali family (with sodium and potassium, among other highly reactive members).  That casts doubt on the second contention of the article.

Some people think if they attach 'Einstein' or 'relativity' to an article that we're supposed to stand back in awe.  He was a super smart guy but there were and are other super smart people out there, too.  How atoms work is more quantum mechanics than relativity and although Einstein played a small role in that subfield, others like Shroedinger and Dirac (to single out just two of many) played much bigger roles.  But most people never heard of them so let's give Einstein all the credit.

(Stepping off my soapbox now....)

[nebulanoodle]

Gold looks more gold to me. Maybe all these scientists describing the colors of things are color blind or maybe they just never had access to the 128 color set of crayons.

[PimentoUK]

Very pure water has a noticeable blue tinge to it. For example the stuff the semiconductor industry use to wash silicon wafers with during IC manufacture. It's not caused by scattering, like the blueness of the sky/sea, it's due to a particular molecular absorption in the middle of the red part of the spectrum, that then leaves the remaining light transmission blue-green tinged.

But apparently, if the hydrogen is replaced by deuterium ( hydrogen with an extra neutron in its nucleus ) it makes clear water. The H atom is heavier, so the O-H bond vibrates at a lower frequency, shifting the red absorption out to the near-infrared. So the visible light passes through the heavy water unimpeded.
I've seen wafer-fab water, and it really is blue. Heavy water is a bit niche, especially super-pure stuff, so I can't verify what that looks, tastes or smells like.

( speaking of taste: one clever bit of science involving heavy water, is the "Doubly-labelled water" experiment, which allows you to evaluate how much energy your body is consuming, by monitoring the water inside you. It needs special water, with deuterium and heavy oxygen to isotopically label it. The CO2 you breathe out means you lose oxygen at a different rate to hydrogen. The harder you work, the more you breathe. By tracking the decay of H and O, it's possible to quite accurately determine energy expenditure. )

[michaelgolden]

Very Interesting thread to say the least!! Although some people may find it quite boring, but they have never had the issues I've had identifying gold!

Here in Minnesota the rivers are full of electrum grade gold. For those unfamiliar with the term "electrum" gold  It's gold that has a high percentage of silver in it. Some of the old timers used to call electrum gold  'Green Gold' BTW.

Usually gold that has over 30 percent silver is considered electrum gold. Most of the gold flake found in the Mn rivers is 40 to 80 percent silver, making it a greenish white color. Far from the nice yellowish color of gold found in rivers out west. For years I could not figure out if this greenish metal flake I found in the bottoms of my gold pans was actually gold (It acted like gold in my gold pan but it's appearance threw me off ..) till I had a few grams of this 'gold' assayed. That's when I found out the truth.. Gold can have a wide variety  of colors. I have  found gold in New Mexico that looked like rose gold as it had a far amount of copper in it, and was quite beautiful to say the least. I have found gold in the black hills that has greenish and  reddish  streaks running thru it. The greenish streaks representing silver and the  reddish streaks representing copper! And again very beautiful in appearance.  Best, Michael

[Valens Legacy]

I had asked my grandfather this same question many years ago and he simply told me that it is yellow because it was scared so much that it hides from us. That is why it is hard to find and that is why it is yellow.

Sounded good to me, so I will guess that it is scared to be seen and that is why we have to hunt it.