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The key parameter which allows one to calculate the effects of Big Bang nucleosynthesis is the baryon/photon number ratio, which is a small number of order 6 × 10 −10. This parameter corresponds to the baryon density and controls the rate at which nucleons collide and react; from this it is possible to calculate element abundances after ...
The abundance of deuterium in Jupiter's atmosphere has been directly measured by the Galileo space probe as 26 atoms per million hydrogen atoms. ISO-SWS observations find 22 atoms per million hydrogen atoms in Jupiter. [16] and this abundance is thought to represent close to the primordial Solar System ratio. [6]
However, if the mineral contains traces of potassium, then decay of the 40 K isotope present will create fresh argon-40 that will remain locked up in the mineral. Since the rate at which this conversion occurs is known, it is possible to determine the elapsed time since the mineral formed by measuring the ratio of 40 K and 40 Ar atoms contained ...
To calculate the binding energy we use the formula Z (m p + m e) + N m n − m nuclide where Z denotes the number of protons in the nuclides and N their number of neutrons. We take m p = 938.272 0813 (58) MeV/ c 2 , m e = 0.510 998 9461 (30) MeV/ c 2 and m n = 939.565 4133 (58) MeV/ c 2 .
(The more massive 209 Bi, long considered to be stable, actually has a half-life of 2.01×10 19 years.) 208 Pb is also a doubly magic isotope, as it has 82 protons and 126 neutrons. [6] It is the heaviest doubly magic nuclide known. A total of 43 lead isotopes are now known, including very unstable synthetic species.
) is a stable isotope of the element helium. It is by far the more abundant of the two naturally occurring isotopes of helium, making up about 99.99986% of the helium on Earth. Its nucleus is identical to an alpha particle, and consists of two protons and two neutrons.
An example is calcium-40, with 20 neutrons and 20 protons, which is the heaviest stable isotope made of the same number of protons and neutrons. Both calcium-48 and nickel-48 are doubly magic because calcium-48 has 20 protons and 28 neutrons while nickel-48 has 28 protons and 20 neutrons. Calcium-48 is very neutron-rich for such a relatively ...
All isotopes of an element have the same number of protons with varying numbers of neutrons. Hydrogen has three naturally occurring isotopes: 1 H, 2 H and 3 H; called protium (H), deuterium (D) and tritium (T), respectively. Both 1 H and 2 H are stable, while 3 H is unstable and beta-decays to 3 He.