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Saturday, February 5, 2011

Periodic Table

My chemistry teacher, a prim matronly Miss Quinn was surprisingly ‘turned on’ by chemistry. We had learned from her that atoms had a small positive nucleus made up of positive protons [and neutral neutrons that are the glue that holds them together] and negative electrons that are really mobile and buzz around in an orderly way, like bees around a hive. Then I remember so clearly the day she introduced the periodic table - I was totally captivated as I grasped the orderliness of the basic elements in all universe! The element number told you the number of protons and electrons they each had and from the placement of an element in the table, you basically knew its properties. If you followed a few simple rules, you even knew how it would behave.

It turns out that Chemistry was all about the giving and taking, or the sharing of electrons between atoms to form what we call bonds. When that happened, entirely new substances are created.

For instance, if you mix hydrogen gas with oxygen gas and give them a spark to get them going, they are so anxious to share electrons that they violently explode, the two gases disappear and liquid water appears. A miracle - but it's an understandable one!

Why is water, H2O, liquid? Oxygen is is #8 in the table so has a nucleus with 8 positive protons that have a strong pull on hydrogen’s shared electron and that makes molecules of water have uneven charges and and they stick together like slippery little magnets.

Cool them down and they move more slowly until they finally stick together forming an open patterned network we call ice that floats because of the holes in its structure. Heat it up, and the molecules move faster, the pattern breaks down, ice melts and finally when hot enough, water molecules move so fast they overcome their attaction for one another and separate to form a gas, water vapour.

Chemisry can get complicated but the more we figure out the rules by which it’s playing, the more logical and understandable and fascinating it becomes.