Au197

Au-197, or gold-197, is a stable isotope of gold with mass number 197 and atomic number 79. It is the only stable and naturally occurring isotope of gold, which means that natural gold is essentially monoisotopic, consisting almost entirely of 197Au.

Nuclear properties and stability: 197Au has 79 protons and 118 neutrons (N = A − Z = 118). It does not undergo radioactive decay under ordinary conditions, which is why it is considered stable. Its ground-state nuclear spin and other detailed nuclear properties exist but are not typically required for general description.

Natural occurrence and abundance: In nature, gold is found predominantly as the native element in ores and alluvial deposits. Because 197Au is stable, natural gold is effectively enriched in this isotope, making it the sole contributor to natural gold’s atomic mass.

Physical and atomic characteristics: The atomic mass of 197Au is about 196.9666 atomic mass units. With an atomic number of 79, these properties place gold in the heavier region of the periodic table, widely valued for its malleability and conductivity.

Production and related isotopes: While 197Au itself is stable, isotopes of gold can be created artificially in nuclear reactors or particle accelerators by neutron capture or other reactions. A common practical example is the production of the short-lived 198Au (half-life about 2.7 days) via irradiation of gold, used in some medical and industrial applications.

Uses and significance: 197Au underpins the extensive use of gold in jewelry, electronics, dentistry, and catalysis, due to its chemical stability and favorable physical properties. Its stability also makes gold valuable as a standard for calibrating instruments and as a reference in isotopic and metallurgical studies.