Atomic Number 3 Element Facts

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Lithium Facts: Li or Element 3

By Anne Marie Helmenstine, Ph.D.

Lithium is the element that is atomic number 3 on the periodic table. These means each atom contains 3 protons. Lithium is a soft, silvery, light alkali metal denoted with the symbol Li. Here are interesting facts about atomic number 3:

• Lithium is the lightest metal and the lightest solid element at ordinary temperature and pressure. The density of the solid near room temperature is 0.534 g/cm³. This means it not only floats on water, but is only about half as dense as it. It is so light, it can even float on oil. It also has the highest specific heat capacity of a solid element. Element number 3 has the highest melting point and boiling point of the alkali metals.
• Element number 3 is soft enough to cut with shears. Freshly cut metal is silver-colored, with a metallic luster. However, moist air quickly corrodes the metal, turning it dull gray and finally black.
• Among its uses, lithium is used in medications for bipolar disorder, to make lithium ion batteries, and to add a red color to fireworks. It's also used in glass and ceramics and to make high temperature lubricant grease. It is a coolant in breeder reactors and a source of tritium when atomic number 3 is bombarded with neutrons.
• Lithium is the only alkali metal that reacts with nitrogen. Yet, it is the least reactive metal in its element group. This is because the lithium valence electron is so close to the atomic nucleus. While lithium metal burns in water, it does not do so as vigorously as sodium or potassium. Lithium metal will burn in air and should be stored under kerosene or in an inert atmosphere, like argon. Don't try to extinguish a lithium fire with water as it will only make it worse!
• Because the human body contains a lot of water, lithium will also burn skin. It is corrosive and should not be handled without protective gear.
• The name for the element comes from the Greek word "lithos", which means "stone". Lithium was discovered in the mineral petalite (LiAISi₄O₁₀). Brazilian naturalist and statesman, Jozé Bonifácio de Andralda e Silva found the stone on the Swedish isle Utö. Although the mineral looked like an ordinary gray rock, it flared red when thrown into a fire. Swedish chemist Johan August Arfvedson determined the mineral contained a previously unknown element. He couldn't isolate a pure specimen, but did produce a lithium salt from petalite in 1817.
• The atomic mass of lithium is 6.941. The atomic mass is a weighted average that accounts for the natural isotope abundance of the element.
• Lithium is believed to be one of only three chemical elements produced in the Big Bang that formed the universe. The other two elements are hydrogen and helium. However, lithium is relatively uncommon in the universe. Scientists believe the reason is that lithium is nearly unstable, with isotopes that have the lowest binding energies per nucleon of any stable nuclides.
• Several isotopes of lithium are known, but the natural element is a mix of two stable isotopes. Li-7 (92.41 percent natural abundance) and Li-6 (7.59 percent natural abundance). The most stable radioisotope is lithium-8, which has a half-life of 838 ms.
• Lithium readily loses its outer electron to form the Li⁺ ion. This leaves the atom with a stable inner shell of two electrons. The lithium ion readily conducts electricity.
• Because of its high reactivity, lithium is not found in nature as a pure element, but the ion is abundant in sea water. Lithium compounds are found in clay.
• Mankind's first fusion reaction involved atomic number 3, in which lithium was used to make hydrogen isotopes for fusion by Mark Oliphant in 1932.
• Lithium is found in trace amounts in living organisms, but its function is unclear. Lithium salts are used to treat bipolar disorder, where they act to stabilize mood.
• Lithium is a superconductor at ordinary pressure at an extremely low temperature. It also superconducts at higher temperatures when the pressure is very high (greater than 20 GPa).
• Lithium displays multiple crystal structures and allotropes. It exhibits a rhombohedral crystal structure (nine layer repeat spacing) around 4 K (liquid helium temperature), transitioning to a face-centered cubic and body-centered cubic structure as the temperature increases.