Tag Archives: elements

Fun Science: The Element Lithium

Lithium is the third element on the periodic table, after hydrogen and helium. It is the lightest metal, and you probably use it every day. The batteries in your phones and laptops and most rechargeable batteries you use are lithium ion batteries.

Lithium is used in batteries because it has the highest electrochemical potential of any element. It is so high that it will split water into hydrogen and oxygen (and violently!). This means there is a lot of energy available to exploit. This is also why laptop batteries can sometimes explode; the batteries are sealed very tightly, but if the seal is broken, air and water vapor will come in contact with the lithium and this is unsafe. 10-15 years ago, there weren’t as many lithium batteries in use, but now they are everywhere. Science has made great strides in improving the configurations of the batteries to give more energy, such as increasing the surface area of the lithium portion. Each time you cycle your battery, the lithium undergoes an electrochemical reaction on the draining and again on the charging of the battery. This is also why batteries become shorter lived over time; the high surface areas of new batteries aren’t thermodynamically favorable, and the lithium will become lower surface area with time. Less available surface area means less available energy.

Lithium ion (Li+) has another, very different use. It is used as a mood stabilizer. It is particularly useful at combatting mania. The linked wikipedia page contains its fascinating medical history. It was first used in the 1870’s as a mood stabilizer. Eventually LiCl was marketed as an alternative to table salt (NaCl), to avoid high blood pressure, and its mood properties were forgotten. Early versions of 7 Up contained lithium. Excessive lithium use was found to be deadly, and it was banned as an additive in the 1940s. Then in Australia, it was again discovered to have mood-stabilizing properties. Its therapeutic dose is quite close to its toxic dose, which is maybe why it took a while to gain approval in the US. Studies suggest that water supplies containing lithium may promote longevity and reduce the occurrence of suicide.

Lithium salts also have another really nifty use: cleansing the air in spaceships and submarines.  Not only does human breathing consume oxygen; it also produces carbon dioxide, which is toxic when present in high amounts. Several lithium salts can remove carbon dioxide from the air. One even adds oxygen to the air when it removes carbon dioxide.

Elemental lithium is highly reactive, and is a member of the alkali metal group (all of whom react very impressively with water). Below is a video of lithium reacting with water. It bursts into bright red flame:

Another video shows more lithium action:

The people who made the second video have a great youtube channel with videos about all the elements done in a university laboratory environment. Most of them have good footage of reactions as well. I just spent an hour watching their videos, they are very entertaining for people with little knowledge, or a lot. If you have a little time to kill, the videos of sodium and potassium are also good, flammable fun.

Fun Science: Why’s platinum so special?

In science, we tend only to learn about a small subset of the elements that populate our world. This is not unreasonable, since 96% of our bodies are composed of just hydrogen, water, carbon, and nitrogen. But there are over a hundred more elements, and they often influence life outside our bodies in ways we don’t hear about. So in today’s post I will talk about platinum.

Platinum is one of the rarest metals in the Earth’s crust. Only 192 tonnes of it are mined annually, where 2700 tonnes of gold are mined annually. When the economy is doing well, platinum can be twice as expensive as gold. So what’s so valuable about it?

Platinum is used a lot in jewelry. Platinum has the appearance of silver, but it doesn’t oxidize and become tarnished like silver. It’s harder than gold, and its rarity can be appealing.

But it’s the chemical properties of platinum that set it apart. Platinum is a great catalyst. This means that platinum facilitates chemical reactions, but is not consumed as the reaction proceeds. The catalytic converter in your car is a platinum catalyst. The catalytic converter helps eliminate a variety of undesirable compounds such as carbon monoxide, nitrous oxides, and incompletely combusted hydrocarbons. Platinum is also a critical part of current hydrogen fuel cells; it splits hydrogen into protons and electrons.

Platinum doesn’t force reactions to occur, but it makes them easier by reducing the energy required. The image below shows the reaction of carbon monoxide (CO) to carbon dioxide (CO2). The chart at the bottom shows the potential energy before, during and after the reaction. Imagine a ball rolling along the red curve (with platinum) and the black curve (without platinum). The ball on the black curve will need more speed to get over the hump. Any given ball is more likely to get over the red hump. Likewise, the presence of platinum lets CO get over the hump to become CO2. Platinum does this for all kinds of reactions.

activation energy

The reaction takes less energy because once a molecule bonds to the surface of platinum, the bonds within the molecule are a little weaker. Molecules like O-O and H-H can split into singletons, something they would never do off the surface. Below I show an example reaction for CO to COon platinum. This diagram is meant to be illustrative, a possible mechanism for the reaction and to show how platinum helps out. In reality these reactions occur very quickly, and careers can be spent figuring out exact reaction mechanisms.

catalysis

 

Platinum is a bit like velcro. Molecules become hooked to the surface, do their reaction, and unstick. If molecules stick and then refuse to unstick, this is called catalyst poisoning, and it’s a big issue in fuel cells. Like velcro, once the hooks are occupied, they can’t do anything else. Platinum is a good catalyst because a lot of things (like hydrocarbons) want to stick to it, but they don’t stick too hard. Other metals either are not attractive enough, or they are too attractive. Platinum is so valuable because, besides being rare, its properties happen to be balanced just right for the reactions we want.