Absolute dating radiocarbon dating. The development of accelerator mass spectrometry (AMS) dating, which allows a date to be obtained from a very small sample, has been very useful in this regard. Other radiometric dating techniques are available for earlier periods. One of the most widely used is potassium–argon dating (K–Ar dating). Potassium-40 is a radioactive isotope of potassium that decays into argon-40. The half-life of potassium-40 is 1.3 billion years, far longer than that of carbon-14, allowing much older samples to be dated. Potassium is common in rocks and minerals, allowing many samples of geochronological or archeological interest to be dated. Argon,
Pertechnetate is found in a Meckel's diverticulum with Meckel's scans. All technetium salts are mildy radioactive, but some of them have explored use of the element for its chemical properties. In these uses, its radioactivity is incidental, and generally the least radioactive (longest-lived) isotopes of Tc are used. In particular, Tc (half-life 211,000 years) is used in corrosion research, because it is the decay product of the easily obtained commercial Tc isotope, which is its nuclear isomer. In theory, the longest-lived technetium isotope, Tc (half-life 4.2 million years), would be the optimal isotope for this use. Solutions of technetate(VII) react with