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Silicon (14 Si) has 25 known isotopes, with mass numbers ranging from 22 to 46. 28 Si (the most abundant isotope, at 92.23%), 29 Si (4.67%), and 30 Si (3.1%) are stable. The longest-lived radioisotope is 32 Si, which is produced by cosmic ray spallation of argon.
For other isotopes, the isotopic mass is usually within 0.1 u of the mass number. For example, 35 Cl (17 protons and 18 neutrons) has a mass number of 35 and an isotopic mass of 34.96885. [7] The difference of the actual isotopic mass minus the mass number of an atom is known as the mass excess, [8] which for 35 Cl is –0.03115.
Further fractionation took place in the formation of the Earth by planetary differentiation: Earth's core, which makes up 31.5% of the mass of the Earth, has approximate composition Fe 25 Ni 2 Co 0.1 S 3; the mantle makes up 68.1% of the Earth's mass and is composed mostly of denser oxides and silicates, an example being olivine, (Mg,Fe) 2 SiO
electron mass: 9.109 383 7139 (28) × 10 −31 kg: 3.1 × 10 −10 [27] muon mass 1.883 531 627 (42) × 10 −28 kg: 2.2 × 10 −8 [28] tau mass 3.167 54 (21) × 10 −27 kg: 6.8 × 10 −5 [29] proton mass 1.672 621 925 95 (52) × 10 −27 kg: 3.1 × 10 −10 [30] neutron mass
Tetramethylsilane is the accepted internal standard for calibrating chemical shift for 1 H, 13 C and 29 Si NMR spectroscopy in organic solvents (where TMS is soluble). In water, where it is not soluble, sodium salts of DSS, 2,2-dimethyl-2-silapentane-5-sulfonate, are used instead.
The mass number, also called the nucleon number, is the number of protons and neutrons in an atomic nucleus.The mass number is unique for each isotope of an element and is written either after the element name or as a superscript to the left of an element's symbol.
mass "The kilogram, symbol kg, is the SI unit of mass. It is defined by taking the fixed numerical value of the Planck constant h to be 6.626 070 15 × 10 −34 when expressed in the unit J s, which is equal to kg m 2 s −1, where the metre and the second are defined in terms of c and ∆ν Cs." [1] The mass of one litre of water at the ...
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.