Tellurium (Te) is an element that is usually obtained as a byproduct of the copper refining process. If you want to get technical, it comes out of the of the anode mud (slime) that is produced during electrolytic refining. Sometimes, though, you can find it in nature. When tellurium is found in nature, it's usually a telluride of something else; it is compounded with another element. For example, a gold-tellurium compound is called a telluride of gold or a gold telluride. This is more commonly known as a calaverite. The most common natural source of commercial tellurium is calaverite dust. Sources conflict on the abundance ranking of tellurium in the Earth's crust; one source says Tellurium is the 78th most common element, while another says it is the 82nd. The most common telluride is hydrogen telluride (probably due to the abundance of hydrogen in our universe).
As mentioned previously, Tellurium is semimetallic. That means that behaves like a metal in some ways, and like a nonmetal in others. Weird, huh? Tellurides are always compounded with metal elements, such as gold, silver, copper, lead, and nickel. Tellurium, when pure, is silver-white. Tellurides may be different colors, however. For example, calaverite is more yellow/gold than tellurium. Both calaverite and pure tellurium have a "metallic luster" though. We know of tellurium and tellurides thanks to the German scientists Franz Joseph Müller von Reichenstein (who discovered tellurium in 1782) and Martin Heinrich Klaproth (who named it in 1798).
Tellurium has several uses. It can be used as an agent to vulcanize rubber. It can be used to protect lead from sulfuric acid. It can be used to turn glass blue, as an insecticide, germicide, or fungicide. The last three uses are probably successful since tellurium is toxic. If you are exposed to 0.01 milligrams of tellurium for every cubic meter of air, you will develop a horrible garlic-tellurium breath. Blech! Tellurium's primary use (other than as a vulcanization agent) is in semiconductor research. This is because tellurium exhibits some interesting conductive properties. Its conductivity differs depending on the alignment of its atoms. Its conductivity also increases when it is exposed to light.
SSMark82 has put tellurium's boiling and melting temperatures in his writeup, but to put it into terms most of us will understand, tellurium melts at 452°C/846°F and boils at 1390°C/2534°F. That's pretty dang hot (for a human)! Tellurium makes green-blue flames when it burns. Burning produces tellurium dioxide (TeO2), which is also produced when tellurium is oxidized with nitric acid. When exposed to chlorine, tellurium forms tellurium dichloride (TeCl2) and tellurium tetrachloride (TeCl4). When oxidized with chromic acid, tellurium produces telluric acid (H2TeO4). A tellurium atom has 52 electrons, 52 protons, and 76 neutrons. With an electron configuration of "[Kr]5s24d105p4", a tellurium atom looks something like this (with the 0's representing electrons):
____________________________________________________
/ \
/ _________0_____________0________ \
/ 0 0 \
| / _____0____0____ \ |
| 0 0 0 0 |
0 / 0 ________ \ \ 0
| 0 / 0 0 0 0 |
| / 0 / ____ \ 0 \ |
| | | 0 / \ | | | |
0 0 0 0 0 == 0 0 0 0 0
| | | | \____/ 0 | | |
| \ 0 \ / 0 / |
| 0 0 0________0 / 0 |
| \ \ 0 / |
0 0 0_____ ____ _____0 0 0
| \ 0 0 / |
\ 0_________ ____________ _________0 /
\ 0 0 /
\______________________________________________________/
NOTES:
- the picture is not drawn to shape
- the picture is not drawn to scale
- the picture places electrons in subshells in their parent shells
- the picture represents electrons with 0's
- the shells of an atom are not visible as rings in reality
- the "==" in the center of the atom represents the nucleus
There are 30 different isotopes of tellurium. Out of the 16 most common, 6 (37.5%), including pure tellurium are stable. The 10 remaining more common isotopes have a half-life ranging from 12.4 minutes to 2.5E21 years. And lastly, just in case you decide to by some tellurium (!), it cost approximately $100 per pound. Ouch!
Sources:
http://chemicalelements.com
http://pearl1.lanl.gov/periodic/elements/52.html
Microsoft Encarta Encyclopedia ®/World English Dictionary ®
TELLURIUM MODEL
I'm going to be building a model of a tellurium atom. If you've got any suggestions, drop me a /msg. As of now, the model will be built with styrofoam for the nucleus, and multi-colored cotton balls for the neutrons and protons. The electrons, which are mini-multi-colored thumbtacks, will be attached onto foamy-styro-cardboard stuff (which are the orbits).