Lithium for a Longer Life

Lithium is the 25^th most abundant element in the Earth's crust, with approximately 20mg of lithium present in every kilogram of crustal material. It is a soft, silvery-white metal that belongs to Group I (alkali metals). It is so highly reactive that when it is cut in air it will quickly corrode before your eyes. In the presence of water, lithium reacts to form hydrogen gas and lithium hydroxide in aqueous solution. Because it is so reactive, lithium does not occur free in nature, it only appears naturally in compounds.

Lithium-6 and lithium-7 were among the three elements synthesized in the Big Bang according to cosmological theory, the other two elements being hydrogen and helium. Lithium is present in cooler, less massive brown dwarf stars but is destroyed in hotter red dwarf stars, so its presence in the stars' line emission (atomic) spectra can be used to differentiate between these two kinds of stars in the so-called 'lithium test'.

Trace amounts of lithium ions are present in the oceans. The total lithium content of seawater is estimated to be 230 billion tonnes, and is present in concentrations of about 0.2 parts per million.
Lithium is also present in trace amounts in plants and animals. Vertebrates contain lithium in concentrations between 21 and 763 parts per billion.

Lithium salts, such as lithium carbonate, have been to shown to be useful as mood-stabilizing drugs. Therapeutically useful amounts of lithium are between 1.0 and 1.2 millimolar, which is only slightly lower than the toxic amount of 1.5 millimolar.

Scientists at the Friedrich Schiller University Jena have just demonstrated that a regular uptake of lithium could lead to a longer life. The scientists studied the impact of lithium in a concentration that is regularly found in ordinary tap water by analyzing the mortality rate in 18 adjacent Japanese municipalities in relation to the amount of lithium contained in tap water from the respective regions. They found that the mortality rate was considerably lower in those municipalities with more lithium in the drinking water.

Reference
Kim Zarse, Takeshi Terao, Jing Tian, Noboru Iwata, Nobuyoshi Ishii, Michael Ristow. Low-dose lithium uptake promotes longevity in humans and metazoans. European Journal of Nutrition, 2011; DOI: 10.1007/s00394-011-0171-x

Further Reading
Elements and Compounds
Metals and Non-metals
Trends in Group I
Electron Configuration
Naming Ionic Compounds
Writing Ionic Formulae
Parts per Million Concentration
Molarity Concentration
Emission (Atomic) Spectra
Isotopes
Relative Atomic Mass

Study Questions

1. What is the atomic number of lithium?
2. What is the simple electron configuration for an atom of lithium?
3. What is the expected charge on a lithium ion? Explain your answer.
4. Write the formula for each of these compounds:
   
   • lithium hydroxide
   • lithium carbonate
5. Write a balanced chemical equation to represent the reaction between lithium metal and water.
6. For each of the following isotopes of lithium, give the number of protons and the number of neutrons present:
   
   • lithium-6
   • lithium-7
7. Given that the relative atomic mass of lithium is 6.941, and assuming lithium-6 and lithium-7 are the only isotopes of lithium present, calculate the abundance of each isotope.
8. Convert the following to concentrations in molL^-1 (M):
   
   • 0.2ppm
   • 1.2millimolar
   • 1.5millimolar
     
   • 21ppb
   • 763ppb
9. If the total lithium content of seawater is estimated to be 230 billion tonnes, and is present in concentrations of about 0.2 parts per million, what is the mass of seawater present on Earth?
10. In the 'lithium test' for stars, what spectral lines do you expect to see in brown dwarf stars that will not be present in red dwarf stars?