Can anyone here explain why nickels retain a bright silver color despite the fact that they are 75% copper? How is it possible for the 25% of nickel in the coin to be the predominant color?
For the very same reason that a relatively small percentage of silver makes gold white gold. White gold is mostly gold, 18k is 75/25, but it's sure silver colored. The technical reason, it's because all metals, even alloys, are crystalline and the lighter colored metal reflects the light more than the darker colored metal making the lighter color dominant.
Nickel has a marked effect on the colour of Cu-Ni allow. The copper as it becomes lighter as nickel is added. Alloy is slivery white from about 15% of nickel and the lustre and purity increases as with nickel content. In addition the effect of the alloying elements like tensile, proof and hot strength. Solidus, liquidus and corrosion resistance increased as well with nickel content although thermal and electrical conductivity decreases. My 50 cents
The color of a metal is not "reflective" ~ chemistry pun~ on the nucleus content ( protons, neutrons, etc.), but on the outer cloud of electrons that comes with metallic bonding. Color comes from the electrons changing shells due to light energy ( all metals are colorless in the dark) edited to add : the type ( gold, silver, nickel, copper) of metal is due to the nucleus composition but the color is electrons.
Electron Band Theory and stuff. Maybe @GDJMSP can translate the link into plain English for us . http://www.webexhibits.org/causesofcolor/9.html
Yes, but they wouldn't pay me for saying it in plain English though Few would collect coins if they were all solid black .
I've been told that I usually do a decent job of explaining scientific concepts in simple terms, but you guys are own with this one. In any case, the linked article actually gives a good explanation. Hopefully someone can do better job of distilling it down to plain English
So why does the light reflected by the nickel molecules overwhelm (to our eye) the light reflected by the copper molecules. Different energy levels or many many more energy levels emitting light from nickel than from copper?
Because metallic bonding is different than the usual covalent ( such as organic ) , ionic ( such as some minerals), in that the nuclei are more together in the center and the electron cloud is on the outside ( yes, I cheated and lied a little in the sentence, as I am trying to put it into PLAIN ENGLISH for the older generations), and it is the electrons that give the color effect to our retinas.
This was the original question - And although it has been answered it's apparently still generating more questions. So I'll try to explain it a different way. What causes the confusion or perhaps I should say lack of understanding with this is how light and the colors we see normally behave. White light is composed of many different colors. And when white light strikes say a red object what happens is this - because the object is red it absorbs all other colors in the light except the red. The red that is in the white light is not absorbed, instead it is reflected and thus that is the color we see the object as being. The exact same thing happens with all other colors except black. Black absorbs all colors and thus what we see is the lack of light being reflected to our eye. This is what happens with most objects. So it stands to reason that if an object is made of something that is 75% one color, then that is the color we should see. Or so we think. But with metal it's different because metal has a different structure than most other objects - it's crystalline in nature - and so it reflects and absorbs the light in a different way. And it also refracts the light because it is crystalline - which most other objects do not do. So it subdues darker colors and exaggerates lighter colors. And then if you throw in toning, or corrosion if you prefer the word, into the mix everything changes yet again because the metal changes from one substance to another and thus it reflects, absorbs, and refracts light differently than it did before. The toning or corrosion interferes with those 3 properties creating light of a different color than what we originally saw and things go back to acting the way things normally do when it comes to color. Different colors are now absorbed, reflected, and refracted depending on how thick the toning/corrosion is. And once the toning gets thick enough all we see is black because all color is then being absorbed by the object.