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We all know what that is, right? Its water. So why is it written all funny? Well, that is actually the chemical formula for water. "Whoa," you say, "I didn't know water was chemistry!" In reality, everything is chemistry, because everything is made up of elements, so everything has a chemical formula.
Chemical formulas tell us what elements are in a substance, and how many of them there are. Let's take another look at water. Remember that each element only has one capital letter, so we can figure out how many elements are in a substance by counting how many capital letters we see. I see a capital H and a capital O, so that's two elements. Hydrogen and Oxygen, actually. Now what about the tiny 2? Well, that tells us how many atoms we have of the capital letter that came before it. In this case, we have 2 Hydrogen atoms. Since there is no number after O, we can just assume there is 1. So we have 2 Hydrogen atoms and 1 Oxygen atom. Cool, huh? A little too fast? Okay, lets practice a few more:
Chemical formulas tell us what elements are in a substance, and how many of them there are. Let's take another look at water. Remember that each element only has one capital letter, so we can figure out how many elements are in a substance by counting how many capital letters we see. I see a capital H and a capital O, so that's two elements. Hydrogen and Oxygen, actually. Now what about the tiny 2? Well, that tells us how many atoms we have of the capital letter that came before it. In this case, we have 2 Hydrogen atoms. Since there is no number after O, we can just assume there is 1. So we have 2 Hydrogen atoms and 1 Oxygen atom. Cool, huh? A little too fast? Okay, lets practice a few more:
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Meet Butane! This gas is what is used in gas grills. Let's break him down the same way we did water.
- I see two capital letters, C and H, so Butane has two elements, Carbon and Hydrogen
- The C has a 4 next to it, so there are 4 Carbon atoms
- The H has a 10 next to it so there are 10 Hydrogen atoms
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'Ok, how about a harder one? This is Potassium Sulfate. Let's break him down.
Pretty easy right? All of the substances we just looked at were compounds, meaning that they are made up of more than one element. If a chemical formula only has one capital letter, you're dealing with just an element.
Now, let's take it one step further. A compound may be made up of two or more elements but they are all bound together as a single substance, like a chain, or a group of connected blocks.
- I see three capital letters, K, S and O, so Potassium Sulfate has three elements, Potassium, Sulfur and Oxygen.
- The K has a 2 after it, so there are 2 Potassium atoms.
- The S doesn't have any number after it, so we assume its just one Sulfur atom
- The O has a 4 after is, to there are 4 Oxygen atoms.
Pretty easy right? All of the substances we just looked at were compounds, meaning that they are made up of more than one element. If a chemical formula only has one capital letter, you're dealing with just an element.
Now, let's take it one step further. A compound may be made up of two or more elements but they are all bound together as a single substance, like a chain, or a group of connected blocks.
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Let's say the group of blocks to the left represents tetraarsenic pentoxtide, a very funny sounding chemical that has 4 atoms of Arsenic and 5 atoms of Oxygen. That compound is like one single chain, each one with 4 atoms of Arsenic and 5 of Oxygen. Here's the chemical formula for tetraarsenic pentoxtide:
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But what is there was a need for more than one of this set? Say we actually had 3 of this compound laying around. We can't just alter the chemical formula, because then it wouldn't be tetraarsenic pentoxide anymore (although it would be worth it to never have to write that name again). So if we can't change the chemical formula, how would we show that we've got three?
The answer is actually really simple. If we consider each set of cubes as one entity with the chemical formula we wrote above, all we have to do write how many sets we have in front of that formula:
The answer is actually really simple. If we consider each set of cubes as one entity with the chemical formula we wrote above, all we have to do write how many sets we have in front of that formula:
TA DA!!! Okay, so maybe that wasn't all that impressive, but it was easy, right? That number out in front is called a coefficient, which is just a fancy way of saying how many sets you have. It's the same thing as writing "3 decks of cards." Each deck of cards is its own deck, with all the cards in it, but I have 3 sets of them. So lets try to break down our 3 sets of tetraarsenic pentoxide the way we did with compounds in the beginning. Careful, though. Now there is a little math involved:
- There are still only two capital letter, only two elements, Arsenic (Ar) and Oxygen (O). That's always the same, regardless of a coefficient.
- Now, as for how many arsenic atoms. In one compound, there are 4 atoms, but we have 3 sets of the compound, so that makes... 12. 12 atoms of Arsenic.
- Use the same logic for Oxygen. If one compound has 5 atoms of Oxygen and I've got 3 sets, that makes 15 total atoms of Oxygen.