Alpha particles consist of two protons and two neutrons (the nucleus of a helium atom). Therefore, Hydrogen is the only element that doesn't contain (and can't emit) an alpha particle.
2-
Helium-4 cannot emit an alpha particle, as an alpha particle is composed of two protons and two neutrons. Helium-4 already has two protons and two neutrons in its nucleus, so it cannot emit an alpha particle.
Helium and hydrogen do not emit alpha particles because they contain only one or two protons in their nuclei respectively, which is insufficient for them to emit an alpha particle consisting of two protons and two neutrons. Alpha decay typically occurs in heavier elements with larger atomic numbers where the nucleus is unstable and emits an alpha particle to reach a more stable configuration.
yrse
Yes, it is possible; example - 224Ac.
they come from the nuclei of an unstable atom.
Beta particle
No, it cannot. Fission is the "splitting" of an atom, and a hydrogen atom will not fission. Some hydrogen atoms have a neutron stuck to the proton in their nucleus. Some even have two neutrons stuck to that proton. These neutrons can be "knocked loose" in something like a nuclear chair reaction in a weapon. The neutrons then can contribute to the building of the nuclear chain reaction. But fission doesn't happen to hydrogen.
The emission of an alpha particle (which is a Helium nucleus) from a radioactive nuclide would decrease its atomic number (z) by two, and its mass number by 4. So for example, Plutonium-239 (z=94) would emit the alpha particle and jump back down the table to Uranium-235 (z=92). It is possible to go up the table (increase atomic number) through certain beta decays.
A nucleus emits a delayed heavy particle, such as an alpha particle, under specific conditions, typically involving beta decay followed by alpha emission. This process often occurs in heavy, unstable nuclei that undergo a series of decay events where the initial beta decay creates a daughter nucleus in an excited state. If this excited nucleus has sufficient energy and the appropriate configuration, it may subsequently emit an alpha particle after a delay, resulting in a delayed heavy particle emission. The delay can be attributed to the time required for the nucleus to transition to a lower energy state before the alpha decay occurs.
Alpha decay and beta decay (both forms of it) are two different types of radioactive decay. The former has a basis in quantum mechanical tunneling, and the latter is mediated by the weak nuclear force (weak interaction). These two decay schemes will not occur together because of what might be called exclusion or blocking. In either decay scheme, the remaining nucleons in the nucleus undergo what might be termed a "renegotiation" of the terms and conditions under which they are stuck together. The changes within the decaying atomic nucleus are so profound from the point of view of the nucleons, those protons and neutrons that make up a nucleus, that they all effectively "feel" it at the same time. This instantaneous "knowing" among the nucleons, probably communicated by the residual strong force (nuclear binding energy), will prevent the other type of decay from taking place when the first one is "happening" to the nucleus.
Alpha decay emits an alpha particle, which consists of two protons and two neutrons. Beta decay emits either an electron (beta minus decay) or a positron (beta plus decay).