Molecular mass Molecular mass Relative molecular mass or molecular weight is the mass of a molecule. It is calculated as the sum of the relative atomic masses of each constituent element multiplied by the number of atoms of that element in the molecular formula. The molecular mass of small to medium size molecules, measured by mass spectrometry, determines stoichiometry. For large molecules such as proteins, methods based on viscosity and light-scattering can be used to determine molecular mass when crystallographic data are not available. Both atomic and molecular masses are usually obtained relative to the mass of the isotope C (carbon 12),
Isotopes of seaborgium Isotopes of seaborgium Seaborgium <nowiki>(</nowiki>Sg) 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 was Sg in 1974. There are 12 known radioisotopes from Sg to Sg and 2 known isomers (Sg and Sg). The longest-lived isotope is Sg with a half-life of 3.1 minutes. "This section deals with the synthesis of nuclei of seaborgium by so-called "cold" fusion reactions. These are processes that create compound nuclei at low excitation energy (~10–20 MeV, hence "cold"), leading to a higher probability of