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Beryllium is the single exception to both rules, due to its low atomic number. [89] All of the alkali metals except lithium and caesium have at least one naturally occurring radioisotope: sodium-22 and sodium-24 are trace radioisotopes produced cosmogenically, [90] potassium-40 and rubidium-87 have very long half-lives and thus occur naturally ...
Lithium metal is soft enough to be cut with a knife. It is silvery-white. In air it oxidizes to lithium oxide. [10] Its melting point of 180.50 °C (453.65 K; 356.90 °F) [13] and its boiling point of 1,342 °C (1,615 K; 2,448 °F) [13] are each the highest of all the alkali metals while its density of 0.534 g/cm 3 is the lowest.
This is a list of chemical elements and their atomic properties, ordered by atomic number (Z). Since valence electrons are not clearly defined for the d-block and f-block elements, there not being a clear point at which further ionisation becomes unprofitable, a purely formal definition as number of electrons in the outermost shell has been used.
Bulk sodium is usually stored in oil or an inert gas. Sodium metal can be easily cut with a knife. It is a good conductor of electricity and heat. Due to having low atomic mass and large atomic radius, sodium is third-least dense of all elemental metals and is one of only three metals that can float on water, the other two being lithium and ...
A chemical element, often simply called an element, is a type of atom which has a specific number of protons in its atomic nucleus (i.e., a specific atomic number, or Z). [ 1 ] The definitive visualisation of all 118 elements is the periodic table of the elements , whose history along the principles of the periodic law was one of the founding ...
Key physical and atomic properties of the alkaline earth metals; Alkaline earth metal Standard atomic weight [n 2] [20] [21] Melting point Melting point Boiling point [4] Boiling point [4] Density (g/cm 3) [22] Electronegativity First ionization energy (kJ·mol −1) Covalent radius [23] Flame test color Beryllium: 9.012182(3) 1560: 1287: 2744
Rubidium is the first alkali metal in the group to have a density higher than water. On Earth, natural rubidium comprises two isotopes : 72% is a stable isotope 85 Rb, and 28% is slightly radioactive 87 Rb, with a half-life of 48.8 billion years – more than three times as long as the estimated age of the universe .
Francium is an alkali metal whose chemical properties mostly resemble those of caesium. [8] A heavy element with a single valence electron, [9] it has the highest equivalent weight of any element. [8] Liquid francium—if created—should have a surface tension of 0.05092 N/m at its melting point. [10]