Ooh, finally, it’s time to talk about elements and compounds.
This is the part where I explain the periodic table. And, as you may know, the periodic table is pretty much the most important table in all of chemistry.
All the little boxes on this “table” are elements, the simplest form of matter. You literally can’t break these down further. What’s the difference between an element and a substance, you ask?
Okay, well, think of it this way. In my post on matter and its forms, I used water as an example of a substance. Water has its own physical and chemical properties, it’s not a mixture of anything, and no matter how many times you divide it up, you’ll still have the same thing.
But water can be divided up into different things chemically.
Introducing the water molecule, one of the most important molecules in nature. This is a version of a ball-and-stick diagram, a very common way to diagram molecules. Honestly, there aren’t really sticks connecting the parts of a molecule, so I like this drawing better.
What are the parts of a molecule? The big red ball is oxygen, an element. Each little blue ball is hydrogen, another element.
They’re also called atoms, but we can talk about atoms later.
Elements are the building blocks of matter. I think the easiest way to conceptualize elements is by thinking of legos.
Here is a very typical starter lego set. For goodness sake, my brother and I have bought this particular set more times than I can count. And there are tons of other different sets out there—Star Wars, Octan, Ninjago, Lego City, Yellow Submarine…hey, they’ve even got Minecraft now.
When you get a Lego set, you typically build something really cool—regardless of whether you followed the instructions or your creation just came out of your imagination. It might look something like this…
Or even this.
Yeah, I’m pretty sure that’s a life-size Lego car. Goodness, the things people can build with enough pieces and inspiration…
Anyway, my point is, there’s one thing all of these Lego creations have in common. They’re all made out of Lego bricks.
Very, very basic Lego bricks, like this one.
And the cool thing about Legos is, there are so many different types of bricks. There are plates, tiles, and very weird-looking pieces that were designed for use in one set and then became hugely popular because of how many different ways they could be fit together and reinvented…
These Lego pieces, these building blocks of the Lego world, are like elements in chemistry. You can’t break them down further. Okay, so maybe you could theoretically chop a Lego brick in half, but that goes against the established “rules” of Lego building.
Same thing in chemistry—chopping an element in half goes against the established rules, and in chemistry, it’s impossible to rebel against those rules of nature.
Just for all you gamers out there, I’ll include a Minecraft example…
This really cool house build is constructed entirely out of blocks. There is literally nothing in Minecraft that’s not constructed out of blocks, just as there is no Lego build that isn’t constructed out of Lego pieces, and nothing in the universe that isn’t constructed out of elements.
Then, there are compounds…substances that can be separated into simpler substances only by chemical means. For example, table sugar.
Sugar is known in chemistry as sucrose. There are a bunch of other names for it, depending on where you get it from—glucose, fructose, lactose, maltose, et cetera, et cetera. Sucrose, in particular, is composed of oxygen, hydrogen, and carbon.
These three elements are strange company. Pure oxygen is combustible and would be poisonous to breathe if not for the nitrogen we inhale as well. Hydrogen is the flammable gas used in rocket launches. Carbon is basically the one thing all life on Earth has in common.
But put them together, and you get the stuff that’s in literally everything sweet.
How’d that happen?
Well, we’re talking about chemical changes now. In another chemistry post, I went over the physical changes matter undergoes. Physical changes involve a change in shape or size, but all the pieces are still basically what they originally were. Like cutting up an apple.
Chemical changes, on the other hand, result in a completely different thing. A completely different type of matter. A completely different substance. Hence, why sugar combines two dangerous elements with carbon and turns them into a dessert delicacy.
An example of a chemical change is what happens when you burn sugar. Burn water, a substance, and it just turns into water vapor. It’s still water.
But burn sugar, and the oxygen and hydrogen—the building blocks of water—escape up into vapor, leaving behind the boring black lumps of carbon. It’s not sugar at all anymore.
What happens in this experiment is that the compound sugar got broken down into its components, water and carbon. That’s the signature mark of a chemical compound. It can be broken down, but only by chemical means.
Carbon, on the other hand, will not break down no matter what you try. Burn it, freeze it, scatter it…it’s still carbon. Because it’s an element, a building block, and it’s against the rules of chemistry to break it.
Ever heard the age-old advice never to mix water and electricity, or you’ll get shocked?
I’m going to venture a guess at why.
According to my textbook, water + electricity becomes hydrogen and oxygen—a chemical change.
And we know that both hydrogen and oxygen are not to be handled at home. Oxygen is combustible and hydrogen is flammable.
Is it any wonder things get a little…explosive…when you tempt this chemical reaction by combining water and electricity?
(Edit: The above explanation on the electrical conductivity of water is my own speculation. Don’t quote me on it! 🙂 )
Oh, by the way, elements are all substances. A substance is just matter that has a uniform and definite composition, meaning it’s the same all the way through. No anomalous building blocks. And that’s practically the definition of elements.
This universe would be so simple if we only had to keep track of three different elements. Though oxygen, hydrogen, and carbon are a pretty good place to start. These three make up the building blocks of every living being on Earth.
In Star Trek, every humanoid alien is carbon-based, meaning like humans. If they want to show us that an alien is really alien, they make it silicon-based, or some other element. So basically, carbon is important.
But the fact is…there are over one hundred known elements. All with different properties, different sizes, different et cetera…how the heck are we supposed to keep track of them all?
That’s what we have the periodic table for. Each element is designated with a two-letter symbol. I had to memorize the first two and last six columns of the periodic table back in chemistry class. I had to know the element name, symbol, and atomic number.
Atomic number? What the heck is that?
It’s another way of telling elements apart. But that’s a story for another day.
You’ll notice that, as far as the element symbols are concerned, some are pretty weird. I mean, how the heck did we get Na from sodium?
I hate to break it to you, but some of these symbols just…don’t…make…sense.
Honestly. Tin is Sn. Lead is Pb. Au, gold, and Cu, copper, are some favorites of mine. I’m pretty sure they make sense according to whatever obscure system the original chemists used to classify everything, but they don’t make sense to me.
Regardless of sense, the atomic symbols are useful—instead of having to write out sodium chloride every single darn time, you can just say NaCl. And sucrose becomes C12H22O11.
I know “sucrose” is probably more convenient to remember, but just wait until we get into the nitty-gritty chemistry. You’ll want to know what elements are in that compound, and element symbols provide a great shorthand for that.
I haven’t decided what’s next up in Thursdays’ global warming posts, but next time around in chemistry we’ll talk about chemical reactions.