Transcript: How Elements Form Compounds

DAVID POGUE (Technology Guru): Sodium: symbol Na; 11 protons and 11 electrons arranged in shells as two, eight and one. Sodium is an alkali metal. Like all the elements in this group, it's desperate to get rid of that extra electron.

THEO GRAY (Chemist and Author): If you cut it quickly,…

DAVID POGUE: I should see some silvery…

THEO GRAY: …you should see a silvery surface inside.

DAVID POGUE: Indeed. Wow.

It slices like cheese, but it's actually a soft metal.

Theo's offered to put on one of his favorite sodium demonstrations. What happens when the pure element dumps its outer electron in a violent altercation with ordinary water?

He insists we wait until nightfall, when the reaction will be most spectacular.

Kids, do not try this at home!

The whole purpose of this contraption is just to dump it into the bucket of water?

THEO GRAY: Yeah. This is a, it's a sodium dumping machine.

DAVID POGUE: All right, let's give this a try. Here we go!

Nice! Oh!

What we're seeing is what happens when sodium's extra electron tears apart water molecules, releasing flammable hydrogen gas—the H in H2O—which explodes when it mixes with air.

The next day, Theo takes it up a notch. As if sodium plus water weren't violent enough, now he wants to combine the same deadly sodium with another lethal element: chlorine, one of the halogens.

The result, he claims, will be a tasty flavoring for a net full of popcorn.

Isn't chlorine deadly poison?

THEO GRAY: Absolutely.

I mean, chlorine, chlorine—they used it as a poison gas in World War I.

DAVID POGUE: It'll be perfectly safe when these two deadly ingredients combine?

THEO GRAY: I didn't say that. I said that after they're combined, the result is perfectly safe. The actual process of combining them is fraught with difficulties.

DAVID POGUE: Okay. And that's why we're dressed up like miners here.

First, a hunk of sodium in a dry metal bowl,then a jet of pure chlorine: surprisingly, no explosion.

Somehow, when these two bad boys of the periodic table come together, they calm down.

At the atomic level, sodium, an alkali metal, had an electron it didn't want, and chlorine, a halogen, wants desperately to grab an electron. Once the handoff was complete, both atoms wound up with full shells, making them stable and able to join together to form a crystal compound we can't live without: sodium chloride, table salt.

Now, I don't exactly see, like, a pile of salt anywhere.

THEO GRAY: No, the salt, most of it went up in the smoke. That is, it went in the popcorn.

DAVID POGUE: It tastes like salt, the good stuff, fresh.

THEO GRAY: Fresh salt.

DAVID POGUE: Only the freshest salt at Theo's farm.

Theo's backyard reactions have given me a crucial insight: how elements come together to form compounds is all about electrons.