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The term helion is a portmanteau of helium and ion, and in practice refers specifically to the nucleus of the helium-3 isotope, consisting of two protons and one neutron. The nucleus of the other (and far more common) stable isotope of helium, helium-4, consisting of two protons and two neutrons, is called an alpha particle or an alpha for short.
Helium is found in large amounts in minerals of uranium and thorium, including uraninite and its varieties cleveite and pitchblende, [20] [137] carnotite and monazite (a group name; "monazite" usually refers to monazite-(Ce)), [138] [139] because they emit alpha particles (helium nuclei, He 2+) to which electrons immediately combine as soon as ...
The helium atom. Depicted are the nucleus (pink) and the electron cloud distribution (black). The nucleus (upper right) in helium-4 is in reality spherically symmetric and closely resembles the electron cloud, although for more complicated nuclei this is not always the case. Helium-4 (4 He) is a stable isotope of the element helium.
After five years of additional experimental work, Rutherford and Hans Geiger determined that "the alpha particle, after it has lost its positive charge, is a Helium atom". [7] [8] [9]: 61 Alpha radiation consists of particles equivalent to doubly-ionized helium nuclei (He 2+) which can gain electrons from passing through matter. This mechanism ...
Helium-4 nuclei are bosons, containing an even number of spin 1 ⁄ 2 particles. This is a direct result of the addition rules for quantized angular momentum. At low temperatures (about 2.17 K), helium-4 undergoes a phase transition : A fraction of it enters a superfluid phase that can be roughly understood as a type of Bose–Einstein condensate .
One curiosity is why alpha particles, helium nuclei, should be preferentially emitted as opposed to other particles like a single proton or neutron or other atomic nuclei. [ note 1 ] Part of the reason is the high binding energy of the alpha particle, which means that its mass is less than the sum of the masses of two free protons and two free ...
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 most common isotope, 4 He, is produced on Earth by alpha decay of heavier elements; the alpha particles that emerge are fully ionized 4 He nuclei. 4 He is an unusually stable nucleus because it is doubly magic. It was formed in enormous quantities in Big Bang nucleosynthesis. Terrestrial helium consists almost exclusively (all but ~2ppm ...