Kr78

Krypton-78, often written as Kr-78, is a stable isotope of the element krypton (atomic number 36). It has 36 protons and 42 neutrons, giving it a mass number of 78. Kr-78 is one of the six stable isotopes of krypton.

In nature krypton exists as a mixture of isotopes, and Kr-78 accounts for a small but detectable portion of atmospheric krypton. Its natural abundance is about 0.35%, with the other stable krypton isotopes—Kr-80, Kr-82, Kr-83, Kr-84, and Kr-86—making up the remainder.

As an even-even nucleus, Kr-78 is expected to have a ground-state spin of 0+ and is not radioactive. Its stability means there is no observed radioactive decay for this isotope under normal conditions.

Kr-78 is primarily encountered as part of naturally occurring krypton in air samples and industrial krypton gas. Isotopic ratios including Kr-78 are measured by mass spectrometry for geochemical and environmental studies, calibration of isotopic dating methods, and tracing applications. However, due to its relatively low abundance, Kr-78 is not typically used as a standalone dating standard.

See also: Krypton; Isotopes of krypton.