What happens during radioactive decay?

Question

What happens during radioactive decay?

Answer 1

The three types of nuclear radioactive decay are alpha, beta and gamma emission.

An alpha particle is a Helium 4 nucleus (two protons and two neutrons). It is produced by nuclear fission in which a massive nucleus breaks apart into two less-massive nuclei (one of them the alpha particle). This is a strong interaction process.

A beta particle is an electron. It emerges from a weak decay process in which one of the neutrons inside an atom decays to produce a proton, the beta electron and an anti-electron-type neutrino. Some nuclei instead undergo beta plus decay, in which a proton decays to become a neutron plus a positron (anti-electron or beta-plus particle) and an electron-type neutrino.

A gamma particle is a photon. It is produced as a step in a radioactive decay chain when a massive nucleus produced by fission relaxes from the excited state in which it first formed towards its lowest energy or ground-state configuration.

Answer 2

Though, origianl molecular compound has tremendoulsy gave of it's high energy after the atom has been splitted or due to chemical reaction, it's an on going reaction that still is radioactive but at much lower energy level given off. What this means is that once, the original reaction has occured the isotopes of the original molecules are still remained to react with whatever it has to react with. The decay is said to have half life and it may take up to 100 years for certain molecules to complete fuflfilled it's required reaction. Good enough, yes?

Answer 3

howstuffworks has a great explanation of this.

see here
http://science.howstuffworks.com/nuclear.htm
and click on
3. radioactive decay.

or just read the entire article and press next at the bottom of the page. you'll get to the part 3 in a few pages.

Answer 4

unstable atomic nuclei emit subatomic particles.

Answer 5

The knowledge and study of radioactive decay goes back to the heroic days of the late 19th century, when scientists became aware of the apparently spontaneous appearance of hitherto unknown "emanations," whose constitutions were initially unknown. Because of the initial mystery surrounding these "emanations," the terms alpha "rays," beta "rays" (these "ray" words later supplanted by "particle"), and gamma-rays were introduced. Only later was it realized that

(A) alpha particles were bare helium nuclei, consisting of 2 protons and 2 neutrons;

(B) beta particles were (at least, first) electrons; and

(C) gamma rays consist of photons; they are very energetic LIGHT.

Radioactive decay can involve emission of either of the FIRST TWO of these "emanations"; the THIRD KIND is sometimes involved as a side issue, but it can also occur when an excited nucleus (perhaps one produced by some previous reaction or radiactive decay) is simply getting rid of excess energy WITHOUT "decaying," that is WITHOUT changing its atomic number or weight.

GENUINE RADIOACTIVE DECAY, involving the first two kinds of particle, can occur as follows:

(A) ALPHA-PARTICLE RADIOACTIVE DECAY: What tends to happen, particularly with the most massive nuclei, is that an alpha particle is spontaneously ejected, and the remaining neutrons and protons re-shuffle, into either :

(i) a single new atomic nucleus of atomic number lower by 2, and the (rounded) atomic weight lower by 4; or

(ii) two new atomic nuclei whose atomic numbers SUM to 2 less than in the original nucleus, and whose (rounded) atomic weights SUM to 4 less than the original value. In this case, the end products tend to be more asymmetric in their properties, rather than both having about half the atomic numbers or weights of the original.

This process occurs "spontaneously" for the most massive nuclei because they have significantly less nuclear binding energy per particle than iron (26Fe56), which is the "most tightly bound" nucleus. (These more massive nuclei are in fact only formed in dynamical late stages of stellar evolution, when nuclei near the "iron peak" are flooded with neutrons, in effect giving the new nuclei excess energy per particle which may only be released anywhere from thousands to many millions, even billions of years later.)

Analogous spontaneous fission emitting alpha particles does occur sometimes for much lower masses. For example, in the CNO cycle of energy generation, an O16 nucleus is briefly produced, but it breaks back very quickly into C12 and He4. (It's that very process that in effect completes the cycle, having processed 4 protons into the alpha particle plus "junk" like positrons, neutrinos and gamma rays.) Since the compound nucleus really doesn't live long enough, its conversion into two distinct atomic nuclei isn't generally described as "radioactive decay." However, it IS the same process, even if it's not described by that term. (A very small fraction of this O16 DOESN'T decay, in fact, resulting in another side cycle so that, only half-jokingly, the whole process ends up being called the CNO "bi-cycle.")

(B) BETA PARTICLE RADIOACTIVE DECAY: For mainly intermediate mass nuclei, in practice, so-called "beta decay" can occur. Most often, this does indeed involve the emission of an ELECTRON, but it can also occur with emission of a POSITRON. In loose terms, this happens when nuclei are respectively "top-heavy" with either NEUTRONS or with PROTONS. (For atomic masses beyond that of hydrogen, the most stable isotopes of nuclei of any atomic weight initially tend to have equal numbers of protons and neutrons. This rough equality gradually changes with increasing atomic mass to favour more neutrons along the so called "valley of beta-stability" in the atomic number/atomic weight plot.)

When an ELECTRON is emitted, a neutron in the original nucleus in effect turns into a proton, INCREASING the atomic number by 1, but not changing its (rounded) atomic weight. When a POSITRON is emitted, a proton in the original nucleus in effect turns into a neutron, DECREASING the atomic number by 1, but not changing its (rounded) atomic weight. (Electron neutrinos or anti-netrinos are also emitted in these radioactive decays.)

Elements on either side of the "valley of beta-stability" can be built up in dynamical, rapidly changing astrophysical situations where there are lots of energetic protons or neutrons around. Subsequently, beta-decay ultimately determines the final consequences. In the case of neutron additions, there are in fact two interesting extremes: the timescale for the addition of neutrons may be "rapid" (r) or "slow" (s) relative to the beta decay timescale of the compound nucleus. This results in noticeable double peaks in abundance (the so-called r-process and s-process peaks) of elements having "magic numbers" of protons or neutrons, when "shells" of protons or neutrons become filled and therefore more tightly bound in the shell model of the nucleus. (This is analogous to a result first found in chemical elements, when electron shells are filled and become more bound than their neighbour atoms.)

(C) As I already remarked, gamma rays (high energy photons) are also emitted during radiactive decay processes, but they tend to be emitted to get rid of excess energy as an excited nucleus settles down towards lower excited energy or ground level nuclear states. There are other ways that nuclei can become excited --- energetic collisions, for example.

So, it is the emission of alpha- or beta-particles, and the changing of atomic numbers and weights that are the hallmark of radiactive decay, andNOT the emission of gamma rays.

Live long and prosper.