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  • The periodic table is instantly recognizable.

  • It's not just in every chemistry lab worldwide,

  • it's found on t-shirts, coffee mugs, and shower curtains.

  • But the periodic table isn't just another trendy icon.

  • It's a massive slab of human genius,

  • up there with the Taj Mahal, the Mona Lisa, and the ice cream sandwich --

  • and the table's creator, Dmitri Mendeleev, is a bonafide science hall-of-famer.

  • But why? What's so great about him and his table?

  • Is it because he made a comprehensive list of the known elements?

  • Nah, you don't earn a spot in science Valhalla just for making a list.

  • Besides, Mendeleev was far from the first person to do that.

  • Is it because Mendeleev arranged elements with similar properties together?

  • Not really, that had already been done too.

  • So what was Mendeleev's genius?

  • Let's look at one of the first versions of the periodic table from around 1870.

  • Here we see elements designated by their two-letter symbols arranged in a table.

  • Check out the entry of the third column, fifth row.

  • There's a dash there.

  • From that unassuming placeholder springs the raw brilliance of Mendeleev.

  • That dash is science.

  • By putting that dash there, Dmitri was making a bold statement.

  • He said -- and I'm paraphrasing here --

  • Y'all haven't discovered this element yet. In the meantime, I'm going to give it a name.

  • It's one step away from aluminum, so we'll call it eka-aluminum,

  • "eka" being Sanskrit for one.

  • Nobody's found eka-aluminum yet, so we don't know anything about it, right?

  • Wrong! Based on where it's located, I can tell you all about it.

  • First of all, an atom of eka-aluminum has an atomic weight of 68,

  • about 68 times heavier than a hydrogen atom.

  • When eka-aluminum is isolated, you'll see it's a solid metal at room temperature.

  • It's shiny, it conducts heat really well,

  • it can be flattened into a sheet, stretched into a wire,

  • but its melting point is low. Like, freakishly low.

  • Oh, and a cubic centimeter of it will weigh six grams.

  • Mendeleev could predict all of these things simply from where the blank spot was,

  • and his understanding of how the elements surrounding it behave.

  • A few years after this prediction,

  • a French guy named Paul Emile Lecoq de Boisbaudran

  • discovered a new element in ore samples

  • and named it gallium after Gaul, the historical name for France.

  • Gallium is one step away from aluminum on the periodic table.

  • It's eka-aluminum. So were Mendeleev's predictions right?

  • Gallium's atomic weight is 69.72.

  • A cubic centimeter of it weighs 5.9 grams.

  • it's a solid metal at room temperature,

  • but it melts at a paltry 30 degrees Celcius,

  • 85 degrees Fahrenheit.

  • It melts in your mouth and in your hand.

  • Not only did Mendeleev completely nail gallium,

  • he predicted other elements that were unknown at the time:

  • scandium, germanium, rhenium.

  • The element he called eka-manganese is now called technetium.

  • Technetium is so rare it couldn't be isolated until it was synthesized in a cyclotron in 1937,

  • almost 70 years after Dmitri predicted its existence,

  • 30 years after he died.

  • Dmitri died without a Nobel Prize in 1907, but he wound up receiving a much more exclusive honor.

  • In 1955, scientists at UC Berkeley successfully created 17 atoms of a previously undiscovered element.

  • This element filled an empty spot in the perodic table at number 101,

  • and was officially named Mendelevium in 1963.

  • There have been well over 800 Nobel Prize winners,

  • but only 15 scientists have an element named after them.

  • So the next time you stare at a periodic table,

  • whether it's on the wall of a university classroom or on a five-dollar coffee mug,

  • Dmitri Mendeleev, the architect of the periodic table,

  • will be staring back.

The periodic table is instantly recognizable.

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B1 中級

TED-ED】メンデレーエフの周期表の天才 - ルー・セリコ (【TED-Ed】The genius of Mendeleev's periodic table - Lou Serico)

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    Zenn に公開 2021 年 01 月 14 日
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