Helium nucleus particles

A positively charged subatomic particle equivalent to a helium nucleus (a). 

The most important types of radioactive particles are alpha particles, beta particles, gamma rays, and X-rays. An alpha particle, which is symbolized as a, is equivalent to a helium nucleus, fHe. Thus, emission of an alpha particle results in a new isotope whose atomic number and atomic mass number are, respectively, 2 and 4 less than that for the unstable parent isotope. 

An alplia p uticle is an energetic helium nucleus. The alplia particle is released from a radioactive element witli a neutron to proton ratio tliat is too low. The helium nucleus consists of two protons and two neutrons. The alplia particle differs from a helimn atom in that it is emitted witliout any electrons. The resulting daughter product from tliis tj pe of transformation lias an atomic number Uiat is two less tluin its parent and an atomic mass number tliat is four less. Below is an e. aiiiple of alpha decay using polonium (Po) polonium has an atomic mass number of 210 (protons and neutrons) and atomic number of 84. 

Alpha particle A helium nucleus He2+ ion, 30 emission, 513 scattering experiment, 26... 

This means that most of the mass of the atom must be furnished by the nucleus. However, the mass of the nucleus is not determined by the number of protons alone. For example, a helium nucleus has two protons and a hydrogen nucleus has one proton. Yet a helium atom is measured to be four times heavier than a hydrogen atom. What can be the composition of the helium nucleus A partial answer to this problem was obtained when a third particle, the neutron, was... 

Now lei us turn to the problem of how the composition of a nucleus affects its stability. The forces that exist between the particles in the nucleus are very large. The most familiar of ihe intranuclear forces is the coulomb force of repulsion which the protons must exert on one another. In order to appreciate the magnitude of this repulsive force, let us compare the force between two protons when they are separated by 10 8 cm, as they are in the hydrogen molecule, with the force between two protons separated by 10-18 cm, as they are in a helium nucleus. In the first case we have... 

There are three common ways by which nuclei can approach the region of stability (1) loss of alpha particles (a-decay) (2) loss of beta particles (/3-decay) (3) capture of an orbital electron. We have already encountered the first type of radioactivity, a-decay, in equation (/0). Emission of a helium nucleus, or alpha particle, is a common form of radioactivity among nuclei with charge greater than 82, since it provides a mechanism by which these nuclei can be converted to new nuclei of lower charge and mass which lie in the belt of stability. The actinides, in particular, are very likely to decay in this way. 

The products are an a-particle (a helium nucleus), and a thorium isotope that is unstable and that rapidly decays by emitting successively two electrons ... 

When Rutherford allowed the radiation to pass between two electrically charged electrodes, he found that one type was attracted to the negatively charged electrode. He proposed that the radiation attracted to the negative electrode consists of positively charged particles, which he called a particles. From the charge and mass of the particles, he was able to identify them as helium atoms that had lost their two electrons. Once Rutherford had identified the atomic nucleus (in 1908, Section B), he realized that an a particle must be a helium nucleus, He2+. An a particle is denoted or simply a. We can think of it as a tightly bound cluster of two protons and two neutrons (Fig. 17.5). 

Alpha Particle—A positively charged particle ejected spontaneously from the nuclei of some radioactive elements. It is identical to a helium nucleus, i.e., 2 neutrons and two protons, with a mass number of 4 and an electrostatic charge of +2. 

Ans. There is no difference. All three are representations of an alpha particle (or a helium nucleus). 

The alpha particle is a helium nucleus produced from the radioactive decay of heavy metals and some nuclear reactions. Alpha decay often occurs among nuclei that have a favorable neutron/proton ratio, but contain too many nucleons for stability. The alpha particle is a massive particle consisting of an assembly of two protons and two neutrons and a resultant charge of +2. 

The alpha particle is a helium nucleus produced from the radioactive decay of heavy metals and some nuclear reactions. 

Alpha (a.) decay. As we shall see later, the alpha particle, which is a helium nucleus, is a stable particle. For some unstable heavy nuclei, the emission of this particle occurs. Because the a particle contains a magic number of both protons and neutrons (2), there is a tendency for this particular combination of particles to be the one emitted rather than some other combination such as s3Li. In alpha decay, the mass number decreases by 4 units, the number of protons decreases by 2, and the number of neutrons decreases by 2. An example of alpha decay is the following ... 

Alpha (a) particles An a particle is composed of two protons and two neutrons, with a charge of +2 essentially, it is a helium nucleus without orbital electrons. Alpha particles usually originate from the nuclear decay of radionuclides of atomic number >82, and are detected in samples containing U, Th, or Ra. Alpha particles react strongly with matter and consequently produce large numbers of ions per unit... 

The ejection of the a particle (labelled as a helium nucleus in the above equation) from the nucleus of element X results in the transmutation of X into Y, which has an atomic number two less than that of X (i.e., two positions below it in the periodic table). The particular isotope of element Y which is formed is that with an atomic mass of four less than that of the original isotope of X. 

An alpha particle is essentially a helium nucleus with two protons and two neutrons. It is represented as (I Ic or a. As this particle leaves the decaying nucleus it has no electrons and thus has a 2+ charge. However, it quickly acquires two electrons from the surroundings to form the neutral atom. Most commonly, we show the alpha particle as the neutral particle and not the cation. 

If a nucleus is too heavy and its atomic number exceeds 82, it may revert to a more stable arrangement by releasing both neutrons and protons. This is effected by the emission of an alpha particle, which contains two protons and two neutrons and is a helium nucleus, 2He2+. 

Scientists initially described radioactivity solely in terms of radiation. The idea of radioactive parf/c/esfirst appeared around the turn of the twentieth century. In 1909, Ernest Rutherford reported confidently that the alpha particle was, in fact, a helium nucleus, jHe, with a 2+ charge. Scientists still had not discovered the proton by this time, so the nature of the helium nucleus (or any other atomic nucleus) was still unknown. In 1919, the existence of the proton was confirmed experimentally by, appropriately enough, Rutherford himself. 

The pure metal of berkelium does not exist in nature and has never been directly artificially produced, although the first isotope of berkelium produced was berkelium-243. It was artificially formed by bombarding americium-241 with the nuclei of helium (alpha particles), as follows " Am+lalpha particle = 2 protons + 2 neutron)—> Bk. (Note Two protons as well as two neutrons are found in the nucleus of helium, and thus the two protons changed the atomic number of americium [ jAm] to berkelium [j Bk].) Today a different process is used to produce berkelium in small amounts, as follows Cm+(5n = neutrons X = gamma rays) —> (becomes) —> Bk + P- = (beta-minus decay). 

Alpha particles are composed of two protons and two neutrons. Thus they have Z = 2, N = 2, and A = 4 and correspond to a helium nucleus He. The emission of a particles thus produces a decrease of 4 units in A. An unstable nuclide undergoing a decay may emit a particles of various energy and thus directly reach the ground level of the stable product. Alternatively, as in )3 emission, an intermediate excited state is reached, followed by y emission. Figure 11.7 shows, for example, the decay process of ioTh., which may directly attain the ground level of by emission of a particles of energy 5.421 MeV or intermediate excited states by emission of a particles of lower energy, followed by y emission. 

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