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Helium is composed of two electrons bound by the electromagnetic force to a nucleus containing two protons along with two neutrons, depending on the isotope, held together by the strong force. Unlike for hydrogen , a closed-form solution to the Schrödinger equation for the helium atom has not been found.
The net binding energy of a nucleus is that of the nuclear attraction, minus the disruptive energy of the electric force. As nuclei get heavier than helium, their net binding energy per nucleon (deduced from the difference in mass between the nucleus and the sum of masses of component nucleons) grows more and more slowly, reaching its peak at iron.
The atomic binding energy of the atom is the energy required to disassemble an atom into free electrons and a nucleus. [4] It is the sum of the ionization energies of all the electrons belonging to a specific atom. The atomic binding energy derives from the electromagnetic interaction of the electrons with the nucleus, mediated by photons.
This simple model reproduces the main features of the binding energy of nuclei. The assumption of nucleus as a drop of Fermi liquid is still widely used in the form of Finite Range Droplet Model (FRDM), due to the possible good reproduction of nuclear binding energy on the whole chart, with the necessary accuracy for predictions of unknown ...
Each proton or neutron's energy state in a nucleus can accommodate both a spin up particle and a spin down particle. Helium-4 has an anomalously large binding energy because its nucleus consists of two protons and two neutrons (it is a doubly magic nucleus), so all four of its nucleons can be in the ground state. Any additional nucleons would ...
Helium-4 nuclear binding per nucleon is stronger than in any of these elements (see nucleogenesis and binding energy) and thus, once helium had been formed, no energetic drive was available to make elements 3, 4 and 5. [93] It is barely energetically favorable for helium to fuse into the next element with a lower energy per nucleon, carbon.
The negative of binding energy per nucleon for nuclides with atomic mass number 125 plotted as a function of atomic number. The profile of binding energy across the valley of stability is roughly a parabola. Tellurium-125 (52 Te) is stable, while antimony-125 (51 Sb) is unstable to β− decay.
Binding energy curve (average binding energy per nucleon in MeV against number of nucleons in nucleus) for a number of relatively common (abundant) isotopes (not chosen systematically; almost anything with an occurence of over .2 was chosen though a few exceptions are in there, such as U235).