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For example, boron trifluoride (BF 3) combines eagerly with fluoride sources to give the tetrafluoroborate anion, BF 4 −. Boron trifluoride is used in the petrochemical industry as a catalyst. The halides react with water to form boric acid. [51] Other boron halides include those with B-B bonding, such as B 2 F 4 and B 4 Cl 4. [55]
Osmium is very rare, substantially more so than any element essential to life. [3] The oxide is toxic to humans. [11] oxygen: 8: 5: Ubiquitous, essential for all forms of life; essentially all biological molecules (not to mention water) contain substantial amounts of oxygen. [11] In high concentrations, oxygen toxicity can occur. palladium: 46: 2a
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This is a list of radioactive nuclides (sometimes also called isotopes), ordered by half-life from shortest to longest, in seconds, minutes, hours, days and years. Current methods make it difficult to measure half-lives between approximately 10 −19 and 10 −10 seconds.
The elements commonly classified as metalloids are boron, silicon, germanium, arsenic, antimony and tellurium. [n 4] The status of polonium and astatine is not settled. Most authors recognise one or the other, or both, as metalloids; Herman, Hoffmann and Ashcroft, on the basis of relativistic modelling, predict astatine will be a monatomic metal.
Thus boron is not a candidate for life. [38] Arsenic is toxic to life, and its possible candidacy has been rejected. [39] [40] In the past (1960s-1970s) other candidates for life were plausible, but with time and more research, only carbon has the complexity and stability to make large molecules and polymers essential for life. [41] [42] [43]
Boron (5 B) naturally occurs as isotopes 10 B and 11 B, the latter of which makes up about 80% of natural boron. There are 13 radioisotopes that have been discovered, with mass numbers from 7 to 21, all with short half-lives, the longest being that of 8 B, with a half-life of only 771.9(9) ms and 12 B with a half-life of 20.20(2) ms.
Alkylideneboranes (RB=CRR) with a boron–carbon double bond are rare. One example, HB=CH 2, can be detected at low temperature. The derivative CH 3 B=C(SiMe 3) 2 is fairly stable, but prone to cyclodimerisation. [19] Some boron-substituted heterocycles are aromatic, but very few such arenes are stable. In borabenzene, boron replaces one CH ...