What nuclear reaction is classified as alpha decay?

Question

Lily Adams · Accepted Answer

An alpha decay is any nuclear reaction in which the mass number decreases by four and the atomic number decreases by two.

Fission causes nuclei to decay via one of three methods: beta, gamma, or alpha.

In an #alpha#-decay, the atomic number (i.e., the number of protons or electrons in a neutral atom) of the parent nucleus decreases by two units while the mass number (the number of protons and neutrons put together) of the nucleus decreases by four units and an #alpha#-particle is emitted, which basically is a Helium-4 nucleus.

Take a look at these instances:

#""_92^238 U -> ""_90^234 Th + ""_2^4 He#

#""_8^16 O + gamma -> ""_6^12 C + ""_2^4 He#

Here, in both the reactions, the parent nuclei breakup to emit an alpha particle (a #""^4 He# nucleus) along with the daughter nucleus. Whereas the first reaction occurs as the # ""_92^238 U# is a comparatively unstable nucleus, in the second reaction, energy is to be given from outside to force the highly stable #""_8^16 O# to breakup in to #""_6^12 C# and an #alpha#. The second example may also be written in short as #""_8^16 O(gamma,alpha)""_6^12 C# reaction.

Nicholas Agrusa · Answer

undefined The nuclear reaction classified as alpha decay involves the emission of an alpha particle from the nucleus of an atom. An alpha particle consists of two protons and two neutrons, which is equivalent to the nucleus of a helium-4 atom. This process reduces the atomic number of the parent atom by two and the mass number by four.