Atomic mass in 12 grams of the carbon isotope C-12. The number of atoms in a mole is called Avogadro's number, the value of which is approximately 6.022 × 10. One mole of a substance always contains almost exactly the "standard atomic weight" or "molar mass" of that substance; however, this may or may not be true for the "atomic mass," depending on whether or not the element exists naturally in more than one isotope. For example, the standard atomic weight of iron is 55.847 g/mol, and therefore one mole of iron as commonly found on earth has a mass of 55.847
Isotopes of nobelium Isotopes of nobelium Nobelium (No) is a synthetic element, and thus a standard atomic weight cannot be given. Like all synthetic elements, it has no stable isotopes. The first isotope to be synthesized (and correctly identified) was No in 1966. There are 12 known radioisotopes, which are No to No and No, and 3 isomers, No, No, and No. The longest-lived isotope is No with a half-life of 58 minutes. The longest-lived isomer is No with a half-life of 1.7 seconds. This cold fusion reaction was first studied in 1979 at the FLNR. Further work in 1988 at the GSI