So, the other day, my three-year-old boy found the glow-in-the-dark stars (on a shelf, higher than he should be reaching of course. Don’t ask). He is amazed by them. Not just because they include R2-D2 and C-3PO but because he could go hide in the pantry (again, don’t ask) and still see the robots he loves to play with. (yes he plays in the pantry, with the door shut, cramped under the shelf, in the dark. I love him so much) So he has become the inspiration for this post. (Also, since we are on the subject of Star Wars, have you seen Rogue One? I still haven’t!! Please don’t think less of me, remember how I said I have kids? Babysitters are hard to come by these days) Now, on to more important matters because who wants to discuss all of the important facts about the new star wars movie and how disney is going to make a killing with all of these new episodes……..
How does this all fit in with chemistry, you say? Well, the glow-in-the-dark stars are all about chemistry. We chemists know it as phosphorescence. What a word right? Well, it needs to sound official. Phosphorescence is all about electrons jumping around. Are you thinking, “But I thought electrons didn’t have knees.” You are correct, they aren’t sentient, though they makeup sentient beings. And they sometimes get a bad reputation. For instance, when they are known as free radicals. They are just doing their job which is to absorb and release energy. Electrons are very gifted. They can be wave-like in nature or particle-like (yes, like a wave. Other waves you are familiar with may include: ocean waves, light waves, sound waves and waves goodbye). They are associated with a proton-neutron nucleus; referring to a central location even though we are pretty sure electrons don’t orbit around like the planets around the sun. Electrons have certain amounts of energy; discrete amounts. That doesn’t mean discreet, as in careful or unoffensive, but discrete as in separate or a certain amount. They can’t absorb just any old amount of energy; it must be a certain amount, calculable by a famous equation based on atomic line spectra of a hydrogen atom and the quantum number of the electron. Did you just tune out? I read somewhere that the most efficient method for clearing short-term memory, the memory you are using right now as you read this stuff, is to do a little math. Why do you think your math teacher makes you practice the same thing over and over? Perhaps it is because you can overcome this memory erasing problem and actually log the info into your brain more permanently with repetition. Maybe. Back to electrons and their quanta……did I just hear you say, “another ridiculous term?”, “What does that even mean?” or “Why can’t chemists speak more clearly or at least use actual words? Mumblers”. Well, remember that discrete amount of energy? It is referred to as a quantum of energy. That is the definition of quantum, a discrete amount. So to sum it all up…..electrons and their quanta (that is plural for quantum, that makes sense right?) are the cause of phosphorescence in those wonderful glow-in-the-dark stars that we all love to put on our ceilings. And if you are as lucky as I am, you have a set with R2-D2 and C-3PO.
So what is happening exactly……..
Do you remember when you had your glow-in-the-dark stuff and you had to “charge it”? Meaning you stood really close to a lamp and held your “glow-in-the-dark whatever” really close to a hot lightbulb so that it would glow really bright? The light given off by that really hot lightbulb is a wave and contains its own amount of energy. Some of those light waves would run into, collide, with an electron which would absorb that amount of energy. This absorption causes the electron to “jump energy levels” or go to an “excited state”. (For some reason that makes me think of Steve in “Cloudy With a Chance of Meatballs”) This just means the electron isn’t home anymore, it has gone for a short vacation away from the nucleus but will be back shortly. When the electron returns from its vacation back to its “ground state” (not grounded, it isn’t in trouble) it releases that quantum of light which you see as “glow-in-the-dark”. Did you notice that some lightbulbs were more effective at “charging” the “Glow-in-the-dark” stars than other lightbulbs? That has to do with the quantum situation. Electrons have and can only have discrete amounts of energy. They aren’t like your car that goes from 0-60 mph in 5 minutes. they are more like a person climbing a flight of stairs. That person can’t take a step halfway between stairs, they would fall back down to the stair they began from. Electrons can only absorb certain wavelengths of light, thus if you shine your red laser pointer on your glow in the dark star it probably won’t “charge it” but your nice fluorescent bulb in the garage will “charge it” nicely due to the correct amount of energy given off by the bulb. Fluorescent bulbs are coated with a fine mercury powder that when charged with electricity gives off light waves in the ultraviolet portion of the light spectrum. (I’m leaving that discussion for an entirely different post) We all know that UV light (that’s the same thing as “ultraviolet”, just so you know) has more energy than a plain old flashlight beam due to the fact that we can get a nice suntan (or bright red burn in my case due to my lack of melanin but I digress……again.). The sun is probably one of the best ways to “charge” your glow-in-the-dark stuff but since it is the middle of winter and my glow-in-the-dark stars are on my ceiling which just can’t get that direct light, I tend to rely on my floor lamp that has a nice luminous bulb in it. I also happen to have a nice bright LED flashlight that works quite well and one of those “micro photon lights” that works nicely also.
Hopefully, your level of appreciation for glow-in-the-dark technology has improved and hopefully, every time you see something made of glow-in-the-dark stuff you will always think of the
wonders of electrons jumping about like sugared-up 4-year olds….in discreet amounts of course.