Lithium is a soft, silvery-white alkali metal. Under standard conditions, it is the lightest metal and the lightest solid element. Like all alkali metals, lithium is highly reactive and flammable, and is stored in mineral oil. Lithium has many applications, from lubricating grease, alloying additions in particular for aluminium and magnesium alloys, to glazes for ceramics, and finally, lithium batteries. The metal is separated from other elements in igneous minerals. The metal is produced through electrolysis from a mixture of fused 55% lithium chloride and 45% potassium chloride at about 450 °C.
Protons and Neutrons in Lithium
Lithium is a chemical element with atomic number 3 which means there are 3 protons in its nucleus. Total number of protons in the nucleus is called the atomic number of the atom and is given the symbol Z. The total electrical charge of the nucleus is therefore +Ze, where e (elementary charge) equals to 1,602 x 10-19 coulombs.
The total number of neutrons in the nucleus of an atom is called the neutron number of the atom and is given the symbol N. Neutron number plus atomic number equals atomic mass number: N+Z=A. The difference between the neutron number and the atomic number is known as the neutron excess: D = N – Z = A – 2Z.
For stable elements, there is usually a variety of stable isotopes. Isotopes are nuclides that have the same atomic number and are therefore the same element, but differ in the number of neutrons. Mass numbers of typical isotopes of Lithium are 6; 7.
Main Isotopes of Lithium
Naturally occurring lithium is composed of two stable isotopes, 6Li and 7Li, the latter being the more abundant (92.5% natural abundance). Lithium-6 is valuable as the source material for the production of tritium (hydrogen-3) and as an absorber of neutrons in nuclear fusion reactions. Natural lithium contains about 7.5 percent lithium-6.
Both natural isotopes have anomalously low nuclear binding energy per nucleon (compared to the neighboring elements on the periodic table, helium and beryllium); lithium is the only low numbered element that can produce net energy through nuclear fission.
7Li is one of the primordial elements (or, more properly, primordial nuclides) produced in Big Bang nucleosynthesis. A small amount of both 6Li and 7Li are produced in stars, but are thought to be “burned” as fast as produced. A lithium-7 atom contains three protons, four neutrons, and three electrons.
Electrons and Electron Configuration
The number of electrons in an electrically-neutral atom is the same as the number of protons in the nucleus. Therefore, the number of electrons in neutral atom of Lithium is 3. Each electron is influenced by the electric fields produced by the positive nuclear charge and the other (Z – 1) negative electrons in the atom.
Since the number of electrons and their arrangement are responsible for the chemical behavior of atoms, the atomic number identifies the various chemical elements. The configuration of these electrons follows from the principles of quantum mechanics. The number of electrons in each element’s electron shells, particularly the outermost valence shell, is the primary factor in determining its chemical bonding behavior. In the periodic table, the elements are listed in order of increasing atomic number Z.
Electron configuration of Lithium is [He] 2s1.
Possible oxidation states are +1.
Lithium reacts with water easily, but with noticeably less vigor than other alkali metals. Lithium is flammable, and it is potentially explosive when exposed to air and especially to water, though less so than the other alkali metals. The lithium-water reaction at normal temperatures is brisk but nonviolent because the hydrogen produced does not ignite on its own. LiHe, a very weakly interacting van der Waals compound, has been detected at very low temperatures.
Most Common Chemical Compound of Lithium
Lithium polymer cells have evolved from lithium-ion and lithium-metal batteries. The primary difference is that instead of using a liquid lithium-salt electrolyte (such as LiPF6) held in an organic solvent (such as EC/DMC/DEC), the battery uses a solid polymer electrolyte (SPE) such as poly(ethylene oxide).
|Number of protons||3|
|Number of neutrons (typical isotopes)||6; 7|
|Number of electrons||3|
|Electron configuration||[He] 2s1|
Properties of other elements