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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.
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 ...
proton mass 1.672 621 925 95 (52) × 10 −27 kg: 3.1 × 10 −10 [30] neutron mass 1.674 927 500 56 (85) × 10 −27 kg: 5.1 × 10 −10 [31] / proton-to-electron mass ratio: 1 836.152 673 426 (32) 1.7 × 10 −11 [32] / W-to-Z mass ratio: 0.881 45 (13) 1.5 × 10 −4 [33]
The ratio of atomic mass to mass number (number of nucleons) varies from 0.998 838 1346 (51) for 56 Fe to 1.007 825 031 898 (14) for 1 H. Any mass defect due to nuclear binding energy is experimentally a small fraction (less than 1%) of the mass of an equal number
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.
Speculated approximate lower limit of the mass of a primordial black hole: 1.5 × 10 −8 kg: US RDA for vitamin D for adults [46] ~2 × 10 −8 kg Uncertainty in the mass of the International Prototype of the Kilogram (IPK) (±~20 μg) [47] 2.2 × 10 −8 kg Planck mass, [48] can be expressed as the mass of a 2 Planck Length radius black hole ...
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However, the relative atomic mass of each isotope is quite close to its mass number (always within 1%). The only isotope whose atomic mass is exactly a natural number is 12 C, which has a mass of 12 Da; because the dalton is defined as 1/12 of the mass of a free neutral carbon-12 atom in the ground state.