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Revisiting the Periodic Table April 8, 2012

Posted by peterxu422 in education, Science, Technology.
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This week on the PBS show NOVA, David Pogue, a New York Times tech columnist, hosted a two hour program titled “Hunting The Elements”. Being the funny goofy person that he is, he made the episode very entertaining filled with fascinating science explained. It is definitely worth a watch for those who have Periodic Table phobia, a term I coined describing those who fear or dislike looking at a periodic table because they do not know how to read one. This program would be great medicine for that.

In the episode, he talks about the reactivity of elements, their origins, their uses, and their properties. In one scene, he goes to an explosion range where he and the fellow scientists test out the explosion speeds of different types of explosive materials like gunpowder, nitrate gel, and C4. He explains that how fast a substance explodes depends on how far away oxygen atoms are from each other within the molecules. Things that burn require oxygen, and so if oxygen is closer to the exploding substance, the reaction can occur more quickly and thus the explosion will be faster. Gunpowder was the slowest one because it has oxygen atoms far away. This is why it’s used to fire projectiles because it has enough force to shoot a projectile out but not enough to destroy the barrel of the gun. C4 is the fastest because the molecules that make up C4 have the oxygen atoms packed closely together.

In another sequence, he visits a bell manufacturing company and makes a whole bronze bell with them. He explains that bronze is made from a combination of copper and tin. Copper is malleable. So if a bell was made of copper and it was struck, it would not create a very good sound since the denting would absorb some of the mechanical energy that would have caused the vibrations to create the sound. Adding tin to the mixture fills up some of the gaps between the copper atoms which would restrict their movement. You get a much sturdier material which is very good for making the resonating rings of bells. Pogue then took a sample of the bell’s material to a lab to see if they had a good mixture of tin and copper. At the lab, they used an electron microscope and magnified the sample to such incredible scales that they were looking at the actual atoms themselves. It showed a very ordered layer of dots where the brighter ones were tin atoms while the darker ones were copper.


Electron microscope image of diamond and silicon

The last sequence I’d like to mention was about shark repellent material. Apparently, the lonely bottom two layers of the Periodic Table, the rare earth metals, have some purpose. These elements are supposedly able to repel sharks. The man who demonstrated this made a large powerful magnet out of one type of rare earth element and when he brought it close to a shark, it immediately turned its head away. They do a few other experiments that clearly illustrate the sharks do not like this material. They suspect the reason for this is that the sharks feel an electric shock when in the presence of this material. When they placed the magnet and a shark fin into a beaker of water, and connected two electric wires from a Voltmeter to it, they showed that a current was flowing. The atoms flowing off the magnet would lose their electrons making them positively charged. These positive ions are then attracted to the shark fin and they flow along it. This stream of moving charges creates a current thus giving a small jolt to the shark. However, the problem I see is that this explanation assumes that the magnet is inside the water. But when they brought the magnet close to the shark form the outer wall of the pool, the shark showed the same reaction. There must be more to the story than the explanation of the electric current.

Finally, to further your experience with the periodic table, I recommend downloading the free iPad app inspired by this program called The Elements. Pogue helped design it himself. It has an interactive Periodic Table, a fun molecule building game, and the whole Hunting the Elements program on it. David Pogue will be replacing Neil deGrasse Tyson as host of NOVA Science Now for the time-being. Dr. Tyson is taking time to film a reboot series of “Cosmos” formerly hosted by Carl Sagan. Pogue is an excellent choice for a host. I had the privilege of meeting him once and he is a very kind and funny person.

VIDEO: Preview for Hunting the Elements

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