165Ho

165Ho is the only stable and naturally occurring isotope of the element Holmium. It has an atomic mass of approximately 164.930637 atomic mass units. The nucleus of 165Ho contains 67 protons and 98 neutrons. This specific composition accounts for its stability, as it does not undergo radioactive decay.

Holmium itself is a rare-earth element with the symbol Ho and atomic number 67. It is classified as a lanthanide and is found in mineral deposits such as monazite and xenotime. While holmium metal is silvery-white and malleable, its primary applications are not directly related to the elemental form but rather to its compounds and the properties of its isotopes.

The significance of 165Ho lies in its role as a benchmark or target material in nuclear physics and medicine. Due to its stability, it can be bombarded with neutrons in a nuclear reactor to produce radioactive isotopes of holmium, most notably 166Ho. This neutron activation process is a key method for generating 166Ho, which has applications in medical imaging and radiotherapy. Therefore, while 165Ho itself is inert, it is a crucial precursor for other holmium isotopes with practical uses. Its abundance and stability make it a readily available starting material for these scientific and medical endeavors.