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Lithium

January 22, 2012

Lithium (Li) is a soft metal, has low density and is highly reactive with water. It has two party tricks. One, when lithium compounds are burnt they burn with a bright red flame – never go to a fireworks display with a chemist, they will suck all the fun out of the experience by telling you which elements have been used to make the different colours. The other trick you may have seen in your chemistry lessons at school. Small lumps of lithium metal would have been cut with a knife from a larger stick and then dropped into a dish of water. The lithium fizzes and skims its way across the surface of the water like a demented water boatman.

To me lithium is like a naïve kid, eager to please and in awe of helium (the cool and aloof distant cousin). Lithium tries to mimic helium by giving away one of its three electrons to any other atom that will take it. As is often the case with two people wearing identical clothes, one will look effortlessly sophisticated, while the other will look faintly ridiculous. Lithium looks ridiculous. Just because lithium is wearing the same number of electrons as helium does not mean they look the same.

Giving away and sharing electrons are how atoms make friends. Losing an electron leaves the atom with a positive charge, in this case Li+, which is attracted to any atom or molecule with a negative charge. Giving away an electron also makes Li+ very small and it is often dwarfed by the atom that has taken its electron making a very uneven pairing. Li+ still sticks loyally to its domineering partner. This generosity means you will never dig up a lump of lithium the way you could a nugget of gold. If most of the lithium on the planet is in the form Li+ we should talk about some of the things Li+ can do.

Lithium’s willingness (or desperate need for appreciation) to give away its electron means it is a great candidate for use in batteries. Electrical energy is simply something that has a charge which is moving. This can be the electron from lithium moving towards another element that will accept it. This is how disposable or coin batteries work. In the rechargeable batteries we have in laptops and mobile phones it is the Li+ that shuttles between the positive and negative ends of the battery (depending on whether it is being charged or being used).

The most unexpected use of lithium is in the treatment of mental illness. Lithium has been found to be most effective in the treatment of Bipolar disorder. Li+ is the active ingredient in the drug lithium carbonate but no one knows exactly how it works. The important bit is that it works and lithium carbonate is the standard by which all new drugs for treating Bipolar disorder are judged. The pharmaceutical use of lithium is all the more surprising because it has no known biological role in the human body. Studies with rats seem to show a need for a very small amount of lithium in their diet (equivalent to about 1mg per day for humans) but the reasons for this are unclear.

Next week’s blog post is to die for! Its Beryllium.

@RotwangsRobot

Images by @SciCommStudios

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