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 dubnium Isotopes of dubnium Dubnium (Db) is a synthetic element, thus a standard atomic weight cannot be given. Like all synthetic elements, it has no stable isotopes. The first isotope to be synthesized was Db in 1968. The 13 known radioisotopes are from Db to Db, and 1–3 isomers. The longest-lived known isotope is Db with a half-life of 29 hours. "This section deals with the synthesis of nuclei of dubnium by so-called "cold" fusion reactions. These are processes which create compound nuclei at low excitation energy (~10–20 MeV, hence "cold"), leading to a higher probability of survival from fission. The