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Astatine is a chemical element; it has symbol At and atomic number 85. It is the rarest naturally occurring element in the Earth's crust, occurring only as the decay product of various heavier elements. All of astatine's isotopes are short-lived; the most stable is astatine-210, with a half-life of 8.1 hours.
All element articles and their infoboxes use IUPAC spelling of elements and compounds. Notably, that is aluminium, sulfur, caesium , not aluminum, sulphur, cesium . For other English variant words (vapor vs. vapour) the infobox reads |engvar= .
Several of the CPK colors refer mnemonically to colors of the pure elements or notable compound. For example, hydrogen is a colorless gas, carbon as charcoal, graphite or coke is black, sulfur powder is yellow, chlorine is a greenish gas, bromine is a dark red liquid, iodine in ether is violet, amorphous phosphorus is red, rust is dark orange-red, etc.
Astatine is the least likely element to ever get any image whatsoever. At least for all the elements below 100, there is something. A picture of a compound, a picture of a very small amount, or an energy emission image. But for astatine, there is nothing.
Astatine compounds are compounds that contain the element astatine (At). As this element is very radioactive, few compounds have been studied. Less reactive than iodine, astatine is the least reactive of the halogens. [1]
Astatine monochloride [7] (AtCl) is made either by the direct combination of gas-phase astatine with chlorine or by the sequential addition of astatine and dichromate ion to an acidic chloride solution. Iodine monobromide (IBr) is made by the direct combination of the elements to form a dark red crystalline solid. It melts at 42 °C and boils ...
In combination with neodymium, another rare-earth element, praseodymium is used to create high-power magnets notable for their strength and durability. [54] In general, most alloys of the cerium-group rare earths ( lanthanum through samarium ) with 3d transition metals give extremely stable magnets that are often used in small equipment, such ...
Chemically, astatine can behave as a halogen (the group of elements including chlorine and fluorine), and could be expected to form ionic astatides with alkali or alkaline earth metals; it is known to form covalent compounds with nonmetals, including other halogens.