The alkalis, or alkali metals, are the group 1 elements of the Periodic Table. In addition to the true metals: lithium (Li), sodium (Na), potassium (K), rubidium (Rb), caesium (Cs), and francium (Fr), hydrogen (H) is usually included.
Each of the elements in group 1 has or may have native mineral occurrences on Earth or elsewhere nearby.
Native hydrogen is not known to occur on the surface of the Earth. As the pressure-temperature phase (PTP) diagram for hydrogen on the left suggests there can be solid metallic monatomic hydrogen and solid H2 at cryogenic temperatures and pressures, including room pressure or atmospheric pressure.
Solid hydrogen (H2) occurs in a hcp structure transitioning to a broken symmetry phase (BSP), then to the A phase at atmospheric pressure with increasing temperature.
As indicated in the magnesium-lithium phase diagram on the left, lithium occurs in the same crystal structure at lower temperatures as it does up to melting temperature. This is the bcc phase (α-Li).
"Native lithium is rare in nature. Most of the lithium is extracted from the mining [of] spodumene."
Lithiophosphate has the chemical formula Li3PO4, with 37.5 at % lithium.
The phase diagram on the left shows bcc (α-Na) at higher temperatures up to melting and hcp (β-Na) with decreasing temperature below the transition at 97.8°C.
Native sodium does not appear to occur on the surface of the Earth.
Halite (NaCl) is probably the most common mineral containing sodium at 50 at %. It is a cubic mineral usually found in arid locations on Earth. Occurrences have clear, white, purple, blue, yellow, orange, and red varieties.
Villiaumite has the chemical formula NaF, with 50 at % sodium.
As indicated in the phase diagram on the left, potassium occurs in a bcc (α-K) phase from room temperature up to melting.
Native potassium does not appear to occur on the Earth's surface.
The pressure-temperature diagram on the left shows that rubidium is bcc (α-Rb) from room temperature through melting.
Native rubidium does not appear to occur on the Earth's surface.
As the temperature-pressure diagram on the left shows, caesium (formerly cesium) is bcc (α-Cs) from room temperature up to melting.
Francium is bcc at room temperature.
- Alkalis, or alkali metals, are the most reactive metals in the Periodic Table.
- Shanghai Xuanshi Machinery Co., Ltd. (2011). "Xuanshi". Shanghai, PRC: Shanghai Xuanshi Machinery Co., Ltd. Retrieved 2015-08-22.
- Willard Lincoln Roberts, George Robert Rapp, Jr., and Julius Weber (1974). Encyclopedia of Minerals. 450 West 33rd Street, New York, New York 10001 USA: Van Nostrand Reinhold Company. p. 693. ISBN 0-442-26820-3.