121Sb

121Sb is a stable isotope of the element antimony (Sb) with a mass number of 121. It is one of the two naturally occurring stable isotopes of antimony, the other being 123Sb. In natural antimony, 121Sb accounts for about 57% of the element’s isotopic composition, with 123Sb making up most of the remainder.

The nucleus of 121Sb contains 51 protons (the atomic number of antimony) and 70 neutrons, giving it an intrinsic stability. Its atomic mass is about 120.9 atomic mass units. As a stable isotope, 121Sb does not undergo radioactive decay and has no radioactive half-life.

Natural occurrence and measurement: 121Sb is found in antimony ores and contributes to the element’s overall atomic mass and chemical properties. The isotope is routinely distinguished from 123Sb in precision mass spectrometry and nuclear physics experiments that require isotopic separation or detailed isotopic ratios.

Applications and significance: Because it is stable, 121Sb has limited direct commercial use tied to its radioactivity. Its primary relevance lies in scientific research, including studies of nuclear structure, isotopic abundances, and materials science where precise isotopic composition can influence measurements. In industry, antimony is typically used in its natural isotopic mix rather than as a single isotope.

See also: isotopes of antimony.