The atomic mass of an atom (i.e., a specific isotope of an element) is measured in comparison with the mass of one atom of carbon-12 (12C) that is assigned a mass of 12 atomic mass units (amu). Atomic mass is sometimes erroneously confused with atomic...

The atomic mass of an element is the mass of the number of particles in its nucleus given in atomic mass units. Although it is sometimes referred to as atomic weight, this is inaccurate, since weight is a measurement that includes the effect of g...

The atomic mass of an element is the mass of the number of particles in its nucleus given in atomic mass units. Although it is sometimes referred to as atomic weight, this is inaccurate, since weight is a measurement that includes the effect of...

The average weight (or mass) of all the isotopes of an element, as determined from the proportions in which they are present in a given element, compared with the mass of the 12 isotopes of carbon (taken as precisely 12,000), which is the official...

The atomic mass (ma) is the mass of an atom at rest, most often expressed in unified atomic mass units.[1] The atomic mass may be considered to be the total mass of protons, neutrons and electrons in a single atom (when the atom is motionless). The...

When a proton captures a neutron to create a nucleus of deuterium, the interaction releases energy in the form of gamma rays. The mass of the resulting nucleus ends up slightly less than the sum of the masses of the individual particles involved....

Researchers have added a chemical element to the periodic table. So far unnamed, this new atom has a nucleus consisting of 112 protons and 165 neutrons, giving it an atomic mass of 277. It's the heaviest nucleus yet created in the laboratory....