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When it comes to learning about the origins of the periodic table...

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...there's just one thing you need to remember.

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The three M's.

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John Mewlands, Dmitri Mendeleev, and Henry Moseley.

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Okay, it's actually John Newlands. But two N's and an M is an awful mnemonic device.

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So let's start with John Newlands.

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Oh, suck it up John. Your achievements are the important thing here.

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A few years before the period table was compiled...

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Newlands noticed that there was something special about the number seven.

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And no, he wasn't a big gambler.

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He realized that there were some uncanny similarities between certain elements.

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All of which had atomic weights that differed by seven.

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He organized the elements using what he called the Law of Octaves.

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Because the way he sorted them looked a bit like octaves of music.

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But it didn't sound nearly as pretty. Even when Newlands would attempt to sing about it in the shower.

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It wasn't until 1869 that Dmitri Mendeleev...

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Oh come on John, your part of the story's over now. Move on.

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It wasn't until 1869 that Mendeleev was playing around with an organization of the elements himself.

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He discovered that when you order them by increasing atomic weight, a pattern seemed to emerge.

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It was always a reactive non-metal, then a very reactive light metal, then a less reactive light metal, and so on.

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He plugged everything into the format we see today.

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Although, not before experimenting with having all like elements in rows, rather than columns.

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Excel spreadsheets probably would have tortured this guy.

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Perhaps the best thing Mendeleev did was to leave spaces for undiscovered elements.

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He'd figure out where there was a missing link and he didn't attempt to stuff something in there that didn't belong.

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By recognizing roughly what should belong in those empty slots...

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Mendeleev was actually able to predict the properties of some of those elements.

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We bet Mr. Newlands would have been awfully jealous.

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Okay, let's wrap this thing up.

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The other big contributor to the periodic table was Henry Moseley.

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Mendeleev still had a couple of question marks on his period table...

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...and it was Moseley who was able to turn those question marks into exclamation points.

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...Well, figuratively speaking.

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After using an X-ray gun to measure the wavelengths, or X-rays...

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Moseley performed a few nifty calculations and concluded that...

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...there was an exact correlation between frequency and atomic number.

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So the few spots that had given Mendeleev a headache finally had an answer.

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Moseley had found the reason why organizing the elements by atomic number...

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...didn't always work out exactly the same as organizing them by atomic mass.

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Even though the modern periodic table is organized by atomic number...because it's pretty darn close.

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Unfortunately, Mendeleev was dead by the time Moseley made his big breakthrough,

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so he never got news of the discovery.

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Huh, you have a really hard time letting things go, don't you there?

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