Nuclear properties

Nuclear properties

By definition, any two atoms with an identical number of protons in their nuclei stk0050 belong to the same chemical element. Atoms with equal numbers of protons but a different number of neutrons are different isotopes of the same element. For example, all hydrogen atoms admit exactly one proton, but isotopes stk4182 exist with no neutrons, one neutron (deuterium), two neutrons (tritium) and more than two neutrons. The known elements form a set of atomic numbers, from the single proton element hydrogen up to the 118-proton element ununoctium.All known isotopes of elements stk621 with atomic numbers greater than 82 are radioactive. About 339 nuclide occur naturally on Earth,of which 255 have not been observed to decay, and are referred to as stable isotopes. However, only 90 of these nuclide are stable to all decay, even in theory. Another 165 (bringing the total to 255) have stm32f103c8t6 not been observed to decay, even though in theory it is energetically possible. These are also formally classified as "stable". An additional 33 radioactive nuclide have half-lives longer than 80 million years, and are long-lived enough to be present from the birth of the solar system. This collection of str54041 288 nuclide are known as primordial nuclide. Finally, an additional 51 short-lived nuclide are known to occur naturally, as daughter products of primordial nuclide decay (such as radium from uranium), or else as products of natural energetic processes on Earth, such as cosmic ray bombardment .