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Tritium (from Ancient Greek τρίτος (trítos) 'third') or hydrogen-3 (symbol T or 3 H) is a rare and radioactive isotope of hydrogen with half-life ~12.3 years. The tritium nucleus (t, sometimes called a triton) contains one proton and two neutrons, whereas the nucleus of the common isotope hydrogen-1 (protium) contains one proton and no neutrons, and that of non-radioactive hydrogen-2 ...
Abundance (atom fraction) of the chemical elements in Earth's upper continental crust as a function of atomic number; [5] siderophiles shown in yellow. Graphs of abundance against atomic number can reveal patterns relating abundance to stellar nucleosynthesis and geochemistry. The alternation of abundance between even and odd atomic number is ...
Rare-earth elements occur in nature in combination with phosphate (monazite), carbonate - fluoride (bastnäsite), and oxygen anions. In their oxides, most rare-earth elements only have a valence of 3 and form sesquioxides (cerium forms CeO2). Five different crystal structures are known, depending on the element and the temperature.
In statistics, the 68–95–99.7 rule, also known as the empirical rule, and sometimes abbreviated 3sr, is a shorthand used to remember the percentage of values that lie within an interval estimate in a normal distribution: approximately 68%, 95%, and 99.7% of the values lie within one, two, and three standard deviations of the mean, respectively.
For helium-3 to form a superfluid, it must be cooled to a temperature of 0.0025 K, or almost a thousand times lower than helium-4 (2.17 K). This difference is explained by quantum statistics , since helium-3 atoms are fermions , while helium-4 atoms are bosons , which condense to a superfluid more easily.
Helium-3 (3He[1][2] see also helion) is a light, stable isotope of helium with two protons and one neutron. (In contrast, the most common isotope, helium-4, has two protons and two neutrons.) Helium-3 and protium (ordinary hydrogen) are the only stable nuclides with more protons than neutrons. It was discovered in 1939.
The concentration of the first hydrolysis product, [Be(H 2 O) 3 (OH)] +, is less than 1% of the beryllium concentration. The most stable hydrolysis product is the trimeric ion [Be 3 (OH) 3 (H 2 O) 6] 3+. Beryllium hydroxide, Be(OH) 2, is insoluble in water at pH 5 or more. Consequently, beryllium compounds are generally insoluble at biological pH.
The +3 and +6 states occur most commonly within chromium compounds, followed by +2; charges of +1, +4 and +5 for chromium are rare, but do nevertheless occasionally exist. [ 26 ] [ 27 ] Common oxidation states