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Bromine monofluoride in ethanol readily leads to the monobromination of the aromatic compounds PhX (para-bromination occurs for X = Me, Bu t, OMe, Br; meta-bromination occurs for the deactivating X = –CO 2 Et, –CHO, –NO 2); this is due to heterolytic fission of the Br–F bond, leading to rapid electrophilic bromination by Br +.
{{Infobox element}}; labels & notes: (Image) GENERAL PROPERTIES Name Symbol Pronunciation (data central) Alternative name(s) Allotropes Appearance <element> IN THE PERIODIC TABLE Periodic table Atomic number Standard atomic weight (data central) Element category (also header bg color) (sets header bg color, over 'series='-color) Group Period ...
Bromine-77 is the most stable radioisotope of bromine, with a half-life of 57 hours. [13] Although β + decay is possible for this isotope, about 99.3% of decays are by electron capture. [ 9 ] Despite its complex emission spectrum, featuring strong gamma-ray emissions at 239, 297, 521, and 579 keV, [ 14 ] 77 Br was used in SPECT imaging in the ...
The mass number (symbol A, from the German word: Atomgewicht, "atomic weight"), [1] also called atomic mass number or nucleon number, is the total number of protons and neutrons (together known as nucleons) in an atomic nucleus. It is approximately equal to the atomic (also known as isotopic) mass of the atom expressed in atomic mass units.
[2] [3] Technetium and promethium (atomic numbers 43 and 61, respectively [a]) and all the elements with an atomic number over 82 only have isotopes that are known to decompose through radioactive decay. No undiscovered elements are expected to be stable; therefore, lead is considered the heaviest stable element.
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 include jumping up and down make it difficult to measure half-lives between approximately 10 −19 and 10 −10 seconds.
Note: All measurements given are in picometers (pm). For more recent data on covalent radii see Covalent radius.Just as atomic units are given in terms of the atomic mass unit (approximately the proton mass), the physically appropriate unit of length here is the Bohr radius, which is the radius of a hydrogen atom.
For each atom, the column marked 1 is the first ionization energy to ionize the neutral atom, the column marked 2 is the second ionization energy to remove a second electron from the +1 ion, the column marked 3 is the third ionization energy to remove a third electron from the +2 ion, and so on.