Hank Green: So, imagine for a second what the would would be like if one day a scientist got up in front of a symposium and stood at the podium and he was like, "Everybody, I've discovered a new letter of the alphabet! It is called frudge, and it belongs between V and W. It's going to be wonderful for making a whole class of new words that have abilities that no word has ever had before." Everybody, welcome to the world of chemistry.

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So, a chemical element is a substance with a particular set of properties that can't be broken down any further than it's already been broken down. Elements are the building blocks of matter; they are the chemist's alphabet. But, unlike the alphabet (which is completely arbitrary -- why does it go A B C D E F G? I... who knows? Who did that? It doesn't have to go in that order), elements are actually set by laws of the universe, so sometimes -- even recently -- we've been able to create new ones. In 2011, we finally got around to naming some elements that were created in the 1990s. Welcome to copernicium! Also darmstadtium and roentgenium (I don't know how to pronounce that one; anybody?).

So we've got now 118 elements, which either just exist on the Earth or have been created in the laboratory, and unsurprisingly it took some doing to get a system together that could organize all that stuff pretty well. But creating a system to organize all of these elements is exactly what Dmitri Ivanovich Mendeleev did. And yeah, he was a Russian dude.

Obviously, this guy was built for science, but not necessarily more so than this guy [Julius Lothar Meyer], or this guy [John Newlands], or this guy [Jean Baptiste Dumas] or this guy [Johann Wolfgang Döbereiner] or this guy [Antoine Lavoisier] or this guy [Louis Pasteur], all of whom made significant contributions to the way that Mendeleev organizing the periodic table.

But what Mendeleev did was almost certainly special, which is why, you know, he has a crater on the Moon named after him and you don't. In Mendeleev's day, only about 60 elements existed, and he really needed some money, so he was writing a chemistry textbook, but he needed a way to organize all of these elements into a table. So he decided, why not sort them by weight, from lightest to heaviest? So Mendeleev started arranging elements into horizontal rows by atomic weight, but he fudged it a little bit to sort elements so that ones with similar physical properties were grouped together. When he did this, a definite pattern started to suggest itself, but only when he left parts of the table blank. And the pattern that he discovered was this.

Elements with similar chemical properties either had really similar atomic weights, like platinum, iridium, and osmium, which are very hard, dense metals and sit next to each other here, or their atomic weights increased in very regular intervals, like in the case of potassium and rubidium and caesium. These are all highly reactive alkali metals, whose atomic weights are each 18 units apart.

So, Mendeleev could see that, if he left some blanks in his table, he could arrange elements horizontally by atomic weight, and if he cut the rows just right, he could group elements with similar properties vertically in the chart as well. Mendeleev was so, sort of, overwhelmed by the power of his discovery here that he not only suggested that those blanks would someday be filled in, he also went so far as to predict what properties and atomic weights those undiscovered elements would have.

And he was really right about his guesses. Absurdly right. He predicted the weights and properties of several elements that were discovered during and after his lifetime, germanium and gallium, probably the most in-your-face examples. Germanium he called "ekasilicon" because it was right below silicon, and gallium he called "ekaaluminum" because it was right below aluminum.

And that is the story of how this beautiful chemical alphabet came to be, and how it is in fact much more logical -- and kind of a lot cooler -- than the alphabet that we traditionally know. So we could all give a big "thank you" to Dmitri Ivanovich Mendeleev. You kick ass.

And if you wanna learn more about Mendeleev, there's a bunch of cool information in the description. You can also ask us questions, which we'll be happy to answer, and suggest other topics for SciShow in the YouTube comments. You can hook up with us on Facebook and Twitter as well. Goodbye.

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