Description: 

The elements had been listed and carefully arranged before Dmitri Mendeleev.

They had even been organized by similar properties before. 

So why is Mendeelev's periodic table the one that has endured?

Lou Serico explains via eka-aluminum, an element whose existence

Mendeelev predicted years before it was discovered. 

Transcription: 

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. 

Questions: 

1. What is a periodic table? 

2. Explain why Mendeleev's periodic table is genius? 

3. What's the name of the number 101 spot in the periodic table?