physical property
Silver white metal. It is soft and can be cut with a knife. It is the lightest metal, and its density is smaller than all oils and liquid hydrocarbons, so it should be stored in solid paraffin or white vaseline (lithium will also float in liquid paraffin).
The density of lithium is very small, only 0.534g/cm ³， It is the smallest of non gaseous simple substances.
Lithium has the smallest compressibility, the largest hardness and the highest melting point compared with other alkali metals because of its small atomic radius.
When the temperature is higher than - 117 ℃, the lithium metal is a typical body centered cubic structure, but when the temperature drops to - 201 ℃, it starts to transform into a face centered cubic structure. The lower the temperature, the greater the transformation degree, but the transformation is incomplete. At 20 ℃, the lattice constant of lithium is 3.50 ｜, and the conductance is about one fifth of that of silver. Lithium easily fuses with any metal other than iron.
The flame reaction of lithium is purple red. [4]
isotope
There are seven isotopes of lithium, two of which are stable, namely Li-6 and Li-7. In addition to the stable isotopes, the longest half-life is Li-8, which has a half-life of 838 milliseconds, followed by Li-9, which has a half-life of 187.3 milliseconds. Other isotopes have a half-life of less than 8.6 milliseconds. Li-4 is the isotope with the shortest half-life among all isotopes, only 7.58043 × 10-23 seconds.
Li-6 has a strong ability to capture low-speed neutrons and can be used to control the speed of nuclear reaction in uranium reactors. It can also be used in radiation protection and prolonging the service life of nuclear missiles, as well as in nuclear powered aircraft and spacecraft in the future. Li-6 can be irradiated by neutrons in nuclear reactors to obtain tritium, which can be used to realize thermonuclear reactions. Li-6 can be used as coolant in nuclear devices
