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Hydrogen is the first, the simplest, the lightest, and the most common element by far. About 90% of all the matter in the universe is hydrogen. Along with carbon and oxygen, it is one of the fundamental building blocks out of which all living things are built.
In pure form, hydrogen is a gas, H2. Because the density of a gas (at a given temperature and pressure) depends mostly on the atomic weight of the atoms or molecules in it, hydrogen is the lightest gas of all. This tempted people to use it for balloons and blimps until the well known Hindenberg disaster, which illustrated that, as a gas, hydrogen is rather flammable. When you burn hydrogen in air, the combustion product is plain water:
2H2 + O2 -> 2H2O
This makes it very attractive as a clean-burning fuel: It's hard to imagine a more friendly energy economy than one based on using solar energy to split water into hydrogen and oxygen, storing the hydrogen, then burning it back into water in cars, fuel cells, etc. The net effect of the whole enterprise would be to transport an insignificant amount of water from the oceans to the cities. Compared to digging up carbon and burning it into carbon dioxide, the environmental impact would be just about nothing.
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  Bottle of Homemade hydrogen.
This is a very Martha Stewart sample: I made it from scratch with two batteries, two paper clips, and a cup of salt water. (Sorry Martha, I did not use flavored sea-salt.)
Making hydrogen gas is actually very easy, and you can read all about how to do it by clicking the story book icon for this sample.
Source: Theodore Gray
Contributor: Theodore Gray
Acquired: 20 August, 2002
Price: $0
Size: 2.5
Purity: >90%
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Tritium location marker.
Tritium is hydrogen with two extra neutrons. That is, the nucleus is one proton and two neutrons instead of just a plain proton like normal hydrogen. Deuterium (see below) is hydrogen with only one extra neutron. Tritium is radioactive, while deuterium and hydrogen are not.
Tritium has two main uses: Thermonuclear weapons and glow in the dark key chains, buttons and exit signs. This particular item is a "location marker" used typically in military situations on ships to make visible the location of obstacles, etc. Tritium is also used as a tracer in certain biochemical reactions, because it can stand in for hydrogen, which is in everything, and you can determine where even vanishingly small quantities of it are by measuring the radioactivity.
Tritium key chains are banned in the US as a "frivolous" use of tritium, but you can legally buy location markers and such like provided you certify that they will be permanently affixed in a stationary location, which is registered with the government. My Periodic Table is such a registered location now, and the marker you see here is screwed down with three spanner-head tamper-proof screws per manufacturers recommendation. (Those frivolous Europeans do not have such limitations, and you can freely buy tritium key chains, tritium fishing lures, probably tritium bellybutton rings if you look hard enough.)
This thing, amazingly, will glow like this for the next twenty years with no batteries, no recharging with room light, no nothing, it just glows. The tritium, with a half-life of 12.5 years, decays emitting an electron, which strikes a phosphor coating inside the glass tube, which in turn emits the green light you see.
It's plainly visible even during the day, if you're in a shadowed corner of the room or cup your hands over it. In the dark it is quite bright.
I was looking at it recently and it's an awe inspiring sight, when you think about how many billions of atoms are decaying every single second to make the billions of photons you see, and that this will keep up every second of every minute for years and decades to come, and it still won't be all out of tritium. And that's in a tiny tube no bigger than the end of your thumb. It really gives you an impression of just how big the number of atoms is, and how small they must be.
While makers of these things claim no radioactivity escapes through the glass, this is only mostly true. I measure about 500 counts per minute, slightly but distinctly above background. Of course, this is about the same level I measure from 4 tablespoons full of salt substitute which people actually buy at the grocery store and then eat (it contains a small percentage of naturally occurring radioactive posassium-40). And it is stopped by a few inches of air. In other words, if you're concerned about it, don't enter the grocery store, because you'll get more there than from this marker.
Source: Ameriglo
Contributor: Theodore Gray
Acquired: 30 August, 2002
Price: $65
Size: 1"
Purity: >90%
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Tritium key chains.
Tritium key chains are banned in the US, along with other "frivolous" uses. And portable devices, like map reading lights, that use tritium can be sold only to law enforcement, military, and emergency response personnel. In Europe and Asia tritium key chains and even fishing lures are popular, and legal for anyone. Go figure.
If you want a tritium key chain, you can buy one on eBay and get it shipped here from the UK, where it is being sold perfectly legally, in less than a week. Of course since it's not legal to possess them here, if I'd done this and had one, would I really be advertising that fact on the internet?
Source: eBay seller marky23uk
Contributor: Theodore Gray
Acquired: 5 September, 2002
Price: $7
Size: 1"
Purity: >90%
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Heavy water.
Deuterium is hydrogen where each nucleus has a neutron as well as the standard proton in it. This makes it basically twice as heavy as normal hydrogen. Heavy water is water (H2O) in which the two hydrogens are replaced by two deuterium atoms. The total molecular weight of heavy water is 20 instead of 18 for normal water, so it's really not all that much heavier.
Deuterium is not radioactive, and for most chemical purposes it is a virtually identical stand in for hydrogen, which means you could probably drink this water and suffer no ill effects. You first.
Click the source link for an interesting story about where this sample came from.
Source: Tryggvi Emilsson and Timothy Brumleve
Contributor: Tryggvi Emilsson and Timothy Brumleve
Acquired: 6 September, 2002
Price: Donated
Size: 1.5"
Purity: 20%
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Sample from the Everest Element Set.
Up until the early 1990's a company in Russia sold a periodic table collection with element samples. At some point their American distributor sold off the remaining stock to a man who is now selling them on eBay. The samples (excepted gasses) weight about 0.25 grams each, and the whole set comes in a very nice wooden box with a printed periodic table in the lid.
To learn more about the set you can visit my page about element collecting for a general description and information about how to buy one, or you can see photographs of all the samples from the set displayed on my website in a periodic table layout or with bigger pictures in numerical order.
Source: Rob Accurso
Contributor: Rob Accurso
Acquired: 7 February, 2003
Price: Donated
Size: 0.2"
Purity: >99%
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Amber with bugs.
I picked this piece of amber out of literally thousands available at a big fossil show because it was really big, really cheap, and it had bugs in it. It's important to have bugs in your amber if you want to extract DNA and recreate dinosaurs, or impress the kids. I'm not sure what distinguishes this amber from other amber that costs a hundred times as much by weight, but I like it.
And it does have some really great bugs! Here's a close-up of one, which is about 1/4 inch in overall size:
I don't really know what the chemical composition of amber is, but it's an organic resin which means it must contain carbon and hydrogen, and I figure it probably contains at least some oxygen, so I've listed it as being composed of those three elements, with carbon being the dominant one. Feel free to correct me if you know better.
Source: Time Trips
Contributor: Theodore Gray
Acquired: 29 March, 2003
Price: $45
Size: 5"
Composition: CHO
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The Universe. (External Sample)
The universe easily meets our criteria for being a reasonably pure sample, as it is about 90% pure hydrogen. As an external sample, this one is not physically located within the table, but rather in its complement. (This is the famous Hubble Deep Field image.)
Location: The Universe
Photographed: 3 October, 2002
Size: 6000000000000000000000000000"
Purity: 90%
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