Naturally occurring

lithium Lithium (from el, λίθος, lithos, lit=stone) is a chemical element with the symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard conditions, it is the least dense metal and the least dense solid el ...

(₃Li) is composed of two

stable isotopes The term stable isotope has a meaning similar to stable nuclide, but is preferably used when speaking of nuclides of a specific element. Hence, the plural form stable isotopes usually refers to isotopes of the same element. The relative abundanc ...

, lithium-6 and lithium-7, with the latter being far more abundant on Earth. Both of the natural

isotopes Isotopes are two or more types of atoms that have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), and that differ in nucleon numbers (mass numbers) ...

have an unexpectedly low

nuclear binding energy Nuclear binding energy in experimental physics is the minimum energy that is required to disassemble the atomic nucleus, nucleus of an atom into its constituent protons and neutrons, known collectively as nucleons. The binding energy for stable n ...

per nucleon ( for lithium-6 and for lithium-7) when compared with the adjacent lighter and heavier elements,

helium Helium (from el, ἥλιος, helios, lit=sun) is a chemical element with the symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas and the first in the noble gas group in the periodic table. ...

( for helium-4) and

beryllium Beryllium is a chemical element with the symbol Be and atomic number 4. It is a steel-gray, strong, lightweight and brittle alkaline earth metal. It is a divalent element that occurs naturally only in combination with other elements to form mi ...

( for beryllium-9). The longest-lived radioisotope of lithium is lithium-8, which has a

half-life Half-life (symbol ) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable ato ...

of just . Lithium-9 has a half-life of , and lithium-11 has a half-life of . All of the remaining isotopes of lithium have half-lives that are shorter than 10 nanoseconds. The shortest-lived known isotope of lithium is lithium-4, which decays by proton emission with a half-life of about (), although the half-life of lithium-3 is yet to be determined, and is likely to be much shorter, like helium-2 (diproton) which undergoes proton emission within s. Lithium-7 and lithium-6 are two of the

primordial nuclides In geochemistry, geophysics and nuclear physics, primordial nuclides, also known as primordial isotopes, are nuclides found on Earth that have existed in their current form since before Earth was formed. Primordial nuclides were present in the ...

that were produced in the

Big Bang The Big Bang event is a physical theory that describes how the universe expanded from an initial state of high density and temperature. Various cosmological models of the Big Bang explain the evolution of the observable universe from the ...

, with lithium-7 to be 10⁻⁹ of all primordial nuclides, and lithium-6 around 10⁻¹³. A small percentage of lithium-6 is also known to be produced by

nuclear reactions In nuclear physics and nuclear chemistry, a nuclear reaction is a process in which two nuclei, or a nucleus and an external subatomic particle, collide to produce one or more new nuclides. Thus, a nuclear reaction must cause a transformation o ...

in certain stars. The isotopes of lithium separate somewhat during a variety of geological processes, including mineral formation (chemical precipitation and ion exchange). Lithium ions replace

magnesium Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ta ...

iron Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in f ...

in certain octahedral locations in

clays Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4). Clays develop plasticity when wet, due to a molecular film of water surrounding the clay par ...

, and lithium-6 is sometimes preferred over lithium-7. This results in some enrichment of lithium-6 in geological processes. Lithium-6 is an important isotope in

nuclear physics Nuclear physics is the field of physics that studies atomic nuclei and their constituents and interactions, in addition to the study of other forms of nuclear matter. Nuclear physics should not be confused with atomic physics, which studies the ...

because when it is bombarded with

neutrons The neutron is a subatomic particle, symbol or , which has a neutral (not positive or negative) charge, and a mass slightly greater than that of a proton. Protons and neutrons constitute the nuclei of atoms. Since protons and neutrons behave ...

, tritium is produced.

List of isotopes

, - , Discovery of this isotope is unconfirmed , style="text-align:right" , 3 , style="text-align:right" , 0 , # , , p ?Decay mode shown is energetically allowed, but has not been experimentally observed to occur in this nuclide. , ? , 3/2−# , , , - , , style="text-align:right" , 3 , style="text-align:right" , 1 , ,
[] , p , Helium-3, , 2− , , , - , , style="text-align:right" , 3 , style="text-align:right" , 2 , ,
[] , p , Helium-4, , 3/2− , , , - , One of the few stable

odd-odd nuclei In nuclear physics, properties of a nucleus depend on evenness or oddness of its atomic number (proton number) ''Z'', neutron number ''N'' and, consequently, of their sum, the mass number ''A''. Most importantly, oddness of both ''Z'' and ''N'' ...

, style="text-align:right" , 3 , style="text-align:right" , 3 , , colspan="3" style="text-align:center;", Stable , 1+ , style="text-align:center" colspan="2", ref name="Atomic Weight of Lithiumb"> , - , style="text-indent:1em" , , colspan="3" style="text-indent:2em" , , , IT , , 0+ , , , - , Produced in Big Bang nucleosynthesis and by cosmic ray spallation , style="text-align:right" , 3 , style="text-align:right" , 4 , , colspan="3" style="text-align:center;", Stable , 3/2− , colspan="2" style="text-align:center", ref name="Atomic Weight of Lithiumb" /> , - , , style="text-align:right" , 3 , style="text-align:right" , 5 , , , β⁻ , Immediately decays into two

α-particles Alpha particles, also called alpha rays or alpha radiation, consist of two protons and two neutrons bound together into a particle identical to a helium-4 nucleus. They are generally produced in the process of alpha decay, but may also be produce ...

for a net reaction of ⁸Li → 2⁴He + e⁻ , 2+ , , , - , rowspan="2", , rowspan="2" style="text-align:right" , 3 , rowspan="2" style="text-align:right" , 6 , rowspan="2", , rowspan="2", , β⁻n () , Immediately decays into two α-particles for a net reaction of ⁹Li → 2⁴He + ¹n + e⁻ , rowspan="2", 3/2− , rowspan="2", , rowspan="2", , - , β⁻ () , , - , , style="text-align:right" , 3 , style="text-align:right" , 7 , ,
[] , n , , (1−, 2−) , , , - , style="text-indent:1em" , , colspan="3" style="text-indent:2em" , , , IT , , 1+ , , , - , style="text-indent:1em" , , colspan="3" style="text-indent:2em" , ,
[] , IT , , 2+ , , , - , rowspan=7, Has 2 halo nucleus, halo neutrons , rowspan=7 style="text-align:right" , 3 , rowspan=7 style="text-align:right" , 8 , rowspan=7, , rowspan=7, , β⁻n () , , rowspan=7, 3/2− , rowspan=7, , rowspan=7, , - , β⁻ () , , - , β⁻2n () , , - , β⁻3n () , Immediately decays into two ⁴He atoms for a net reaction of ¹¹Li → 2⁴He + 3¹n + e⁻ , - , β⁻α () , , - , β⁻d () , , - , β⁻t () , , - , , style="text-align:right" , 3 , style="text-align:right" , 9 , , , n ? , ? , (1−, 2−) , , , - , , style="text-align:right" , 3 , style="text-align:right" , 10 , ,
[] , 2n , , 3/2−# , ,

Isotope separation

Colex separation

Lithium-6 has a greater affinity than lithium-7 for the Chemical element, element mercury (element), mercury. When an amalgam of lithium and mercury is added to solutions containing lithium hydroxide, the lithium-6 becomes more concentrated in the amalgam and the lithium-7 more in the hydroxide solution. The colex (column exchange) separation method makes use of this by passing a counter-flow of amalgam and hydroxide through a cascade of stages. The

fraction A fraction (from la, fractus, "broken") represents a part of a whole or, more generally, any number of equal parts. When spoken in everyday English, a fraction describes how many parts of a certain size there are, for example, one-half, eight ...

of lithium-6 is preferentially drained by the mercury, but the lithium-7 flows mostly with the hydroxide. At the bottom of the column, the lithium (enriched with lithium-6) is separated from the amalgam, and the mercury is recovered to be reused with fresh

raw material A raw material, also known as a feedstock, unprocessed material, or primary commodity, is a basic material that is used to produce goods, finished goods, energy, or intermediate materials that are feedstock for future finished products. As feedst ...

. At the top, the lithium hydroxide solution is electrolyzed to liberate the lithium-7 fraction. The enrichment obtained with this method varies with the column length and the flow speed.

Vacuum distillation

Lithium is heated to a temperature of about in a

vacuum A vacuum is a space devoid of matter. The word is derived from the Latin adjective ''vacuus'' for "vacant" or "void". An approximation to such vacuum is a region with a gaseous pressure much less than atmospheric pressure. Physicists often dis ...

. Lithium atoms evaporate from the liquid surface and are collected on a cold surface positioned a few centimetres above the liquid surface. Since lithium-6 atoms have a greater

mean free path In physics, mean free path is the average distance over which a moving particle (such as an atom, a molecule, or a photon) travels before substantially changing its direction or energy (or, in a specific context, other properties), typically as a ...

, they are collected preferentially. The theoretical separation efficiency is about 8.0 percent. A multistage process may be used to obtain higher degrees of separation.

Lithium-3

Lithium-3, also known as the triproton, would consist of three

protons A proton is a stable subatomic particle, symbol , H+, or 1H+ with a positive electric charge of +1 ''e'' elementary charge. Its mass is slightly less than that of a neutron and 1,836 times the mass of an electron (the proton–electron mass ...

and zero

. It was reported as proton unbound in 1969, but this result was not accepted and its existence is thus unproven. No other resonances attributable to have been reported, and it is expected to decay by prompt proton emission (much like the

diproton Although there are nine known isotopes of helium (2He) (standard atomic weight: ), only helium-3 () and helium-4 () are stable. All radioisotopes are short-lived, the longest-lived being with a half-life of . The least stable is , with a half-lif ...

, ).

Lithium-4

Lithium-4 contains three protons and one neutron. It is the shortest-lived known isotope of lithium, with a half-life of () and decays by proton emission to

helium-3 Helium-3 (3He see also helion) is a light, stable isotope of helium with two protons and one neutron (the most common isotope, helium-4, having two protons and two neutrons in contrast). Other than protium (ordinary hydrogen), helium-3 is the ...

. Lithium-4 can be formed as an intermediate in some nuclear fusion reactions.

Lithium-6

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. Between 1.9% and 7.8% of terrestrial lithium in normal materials consists of lithium-6, with the rest being lithium-7. Large amounts of lithium-6 have been separated out for placing into

thermonuclear weapons A thermonuclear weapon, fusion weapon or hydrogen bomb (H bomb) is a second-generation nuclear weapon design. Its greater sophistication affords it vastly greater destructive power than first-generation nuclear bombs, a more compact size, a lowe ...

. The separation of lithium-6 has by now ceased in the large

thermonuclear Thermonuclear fusion is the process of atomic nuclei combining or “fusing” using high temperatures to drive them close enough together for this to become possible. There are two forms of thermonuclear fusion: ''uncontrolled'', in which the re ...

powers, but stockpiles of it remain in these countries. The

deuterium–tritium fusion Deuterium–tritium fusion (sometimes abbreviated D+T) is a type of nuclear fusion in which one deuterium nucleus fuses with one tritium nucleus, giving one helium nucleus, one free neutron, and 17.6 MeV of energy. It is the most efficient type of ...

reaction has been investigated as a possible energy source, as it is currently the only fusion reaction with sufficient energy output for feasible implementation. In this scenario, lithium enriched in lithium-6 would be required to generate the necessary quantities of tritium. Mineral and brine lithium resources are a potential limiting factor in this scenario, but seawater can eventually also be used. Pressurized heavy-water reactors such as the

CANDU The CANDU (Canada Deuterium Uranium) is a Canadian pressurized heavy-water reactor design used to generate electric power. The acronym refers to its deuterium oxide ( heavy water) moderator and its use of (originally, natural) uranium fuel. C ...

produce small quantities of tritium in their coolant/moderator from neutron absorption and this is sometimes extracted as an alternative to the use of Lithium-6. Lithium-6 is one of only three stable isotopes with a

spin Spin or spinning most often refers to: * Spinning (textiles), the creation of yarn or thread by twisting fibers together, traditionally by hand spinning * Spin, the rotation of an object around a central axis * Spin (propaganda), an intentionally b ...

of 1, the others being

deuterium Deuterium (or hydrogen-2, symbol or deuterium, also known as heavy hydrogen) is one of two Stable isotope ratio, stable isotopes of hydrogen (the other being Hydrogen atom, protium, or hydrogen-1). The atomic nucleus, nucleus of a deuterium ato ...

and

nitrogen-14 Natural nitrogen (7N) consists of two stable isotopes: the vast majority (99.6%) of naturally occurring nitrogen is nitrogen-14, with the remainder being nitrogen-15. Fourteen radioisotopes are also known, with atomic masses ranging from 10 to 25, ...

, and has the smallest nonzero nuclear electric quadrupole moment of any stable nucleus.

Lithium-7

Lithium-7 is by far the most abundant isotope of lithium, making up between 92.2% and 98.1% of all terrestrial lithium. A lithium-7 atom contains three protons, four neutrons, and three electrons. Because of its nuclear properties, lithium-7 is less common than

carbon Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent In chemistry, the valence (US spelling) or valency (British spelling) of an element is the measure of its combining capacity with o ...

nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...

, or

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...

in the Universe, even though the latter three all have heavier nuclei. The industrial production of lithium-6 results in a waste product which is enriched in lithium-7 and depleted in lithium-6. This material has been sold commercially, and some of it has been released into the environment. A relative abundance of lithium-7, as high as 35 percent greater than the natural value, has been measured in the ground water in a carbonate aquifer underneath the West Valley Creek in

Pennsylvania Pennsylvania (; ( Pennsylvania Dutch: )), officially the Commonwealth of Pennsylvania, is a state spanning the Mid-Atlantic, Northeastern, Appalachian, and Great Lakes regions of the United States. It borders Delaware to its southeast, ...

, which is downstream from a lithium processing plant. The isotopic composition of lithium in normal materials can vary somewhat depending on its origin, which determines its relative atomic mass in the source material. An accurate relative atomic mass for samples of lithium cannot be measured for all sources of lithium. Lithium-7 is used as a part of the molten lithium fluoride in molten salt reactors: liquid-fluoride

nuclear reactors A nuclear reactor is a device used to initiate and control a fission nuclear chain reaction or nuclear fusion reactions. Nuclear reactors are used at nuclear power plants for electricity generation and in nuclear marine propulsion. Heat from nu ...

. The large neutron absorption cross section of lithium-6 (about 940

barns A barn is an agricultural building usually on farms and used for various purposes. In North America, a barn refers to structures that house livestock, including cattle and horses, as well as equipment and fodder, and often grain.Allen G. N ...

) as compared with the very small neutron cross section of lithium-7 (about 45 millibarns) makes high separation of lithium-7 from natural lithium a strong requirement for the possible use in lithium fluoride reactors. Lithium-7 hydroxide is used for alkalizing of the coolant in pressurized water reactors. Some lithium-7 has been produced, for a few picoseconds, which contains a lambda particle in its nucleus, whereas an atomic nucleus is generally thought to contain only neutrons and protons.

Lithium-8

Lithium-8 has been proposed as a source of 6.4 MeV electron antineutrinos generated by the inverse beta decay to Beryllium-8. The ISODAR

particle physics Particle physics or high energy physics is the study of fundamental particles and forces that constitute matter and radiation. The fundamental particles in the universe are classified in the Standard Model as fermions (matter particles) an ...

collaboration describes a scheme to generated Lithium-8 for immediate decay by bombarding stable Lithium-7 with 60 MeV protons created by a cyclotron particle accelerator.

Lithium-11

Lithium-11 is thought to possess a halo nucleus consisting of a core of three protons and eight neutrons, two of which are in a nuclear halo. It has an exceptionally large cross-section of 3.16 fm², comparable to that of . It decays by beta emission and neutron emission to , , or (see tables above and below).

Lithium-12

Lithium-12 has a considerably shorter half-life. It decays by neutron emission into , which decays as mentioned above.

Decay chains

While β⁻ decay into isotopes of beryllium (often combined with single- or multiple-neutron emission) is predominant in heavier isotopes of lithium, and decay via neutron emission into and respectively due to their positions beyond the neutron drip line. Lithium-11 has also been observed to decay via multiple forms of fission. Isotopes lighter than decay exclusively by proton emission, as they are beyond the proton drip line. The decay modes of the two isomers of are unknown. :

\begin\\
\ce \\
\ce \\
\ce \\
\ce \\
\ce \\
\ce \\
\ce \\
\ce \\
\ce \\
\ce \\
\ce \\
\ce \\
\ce \\
\ce \\
\end

References

External links

{{Navbox element isotopes Lithium

Lithium Lithium (from el, λίθος, lithos, lit=stone) is a chemical element with the symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard conditions, it is the least dense metal and the least dense solid el ...