Elements

I saw an interesting blog today where someone (an organic chemist) had counted how many different elements he had worked with. Now, a lot of the ensuing discussion can depend on how you define "working" with an element. I'm having trouble putting a specific definition into words, but let's just say that I know it when I see it. In general, the element in question needs to have been a deliberate and important part of what was going on. So, here's what I've used, and, if I feel like it, what I've done.

1: Hydrogen - I've collected H2 gas off of a reaction using HCl, and also ignited H2-filled soap bubbles.
2: Helium - Does inhaling it from balloons count? Even if it didn't, I've put it through a diffraction grating and looked at it spectral lines. That one experiment from physics 107/150 is going to get me a whole handful of these.
3: Carbon - A whole semester of organic chemistry lab. Ewwww.
4: Nitrogen - Liquid nitrogen, for everything from shattering pennies, to making ice cream, to hammering rubber hoses into a 2x4, to actual productive purposes.
5: Oxygen - I've collected it out of the atmosphere as a liquid. Liquid O2 is very exciting. (And potentially very dangerous. I've never had more than a few mL of it.)
6: Fluorine - I use HF at work all the time. The first on this list that I haven't encountered in elemental form.
7: Sodium - It burns yellow. (Like the sun.) I've only burned it in solution though. Elemental sodium is quite dangerous.
8: Magnesium - Burns extremely bright white. It's what they use in fireworks, and it's fun to play around with strips of it. As a side note, water catalyzes it's oxidation, so be very careful how you fight a magnesium fire.
9: Aluminum - Drinking a can of Coke does not fill this requirement. But writing a senior thesis about microscopy of aluminum oxide does.
10: Silicon - More microscopy. And hours spent wedging it down until it is 0.000004 inches thick.
11: Phosphorus, 12: Sulfur, 13: Chlorine: As it turns out, a mixture of these 3 elements (as H3PO4, H2SO4 and HCl) will put holes in your pants quite nicely. Not quite the experiment that I was supposed to be doing, but it's the one that I remember.
14: Argon - this is what we use for an inert atmosphere at work.
15: Calcium - I've dissolved calcium carbonate in acid. Sounds exciting, but it's just limestone.
16: Iron - Well, who hasn't done something with iron?
17: Cobalt - The aluminum oxide I mentioned earlier, well, it was covered in cobalt.
18: Copper - Pennies aren't just for spending, they're also good to turn into brass.
19: Zinc - You take the old penny, disolve some zinc in acid, and, um . . . I forget the rest of the lab, but it ends up with a brass penny.
20: Gallium - it melts near room temperature, so it makes a nice phase transition lab for pre-med students. It also super cools pretty well, unless the surface of your sample is too oxidized, then it just won't re-solidify. And I use it at work all the time.
21: Germanium - I know thee well.
22: Zirconium - Used a strip of it as a heating element once upon a time. It had just the right resistivity.
23: Molybdenum - Hard to spell, and boring to measure the resistivity of a wire made of it! By this point in the periodic table, I'm now skipping the majority of the elements.
24: Indium - I've soldered with it to make electrical contacts.
25: Tin - Also used in soldering.
26: Cesium - I've measured the half-life of a radio active isotope.
27: Tungsten - My wedding ring is made of tungsten carbide. It doesn't scratch. I've tried. Yeah, it's a bit weak, but I'm counting this one.
28: Silver - I have deposited a film of silver onto glass to make my own mirror, which was then used in an experiment to measure the speed of light through different mediums. The experiement was a big failure, but it wasn't the mirror's fault.
29: Mercury - I've studied the spectral lines.
30: Lead - I've measured the half-thickness for stopping the radiation from the aforementioned Cesium isotope.

And, from here on out, pretty much everything is radioactive. There is one other radioactive isotope that I have worked with, but I can't remember what it was. Possibly it was a repeat, but I don't think it was. So, at this point, I can point to 30 elements I've used. There's probably another 1-3 that I have used, but I'm not remembering it at the moment.