What is Radioactive: Definition and 391 Discussions

Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is considered radioactive. Three of the most common types of decay are alpha decay (𝛼-decay), beta decay (𝛽-decay), and gamma decay (𝛾-decay), all of which involve emitting one or more particles or photons. The weak force is the mechanism that is responsible for beta decay, while the other two are governed by the usual electromagnetic and strong forces.Radioactive decay is a stochastic (i.e. random) process at the level of single atoms. According to quantum theory, it is impossible to predict when a particular atom will decay, regardless of how long the atom has existed. However, for a significant number of identical atoms, the overall decay rate can be expressed as a decay constant or as half-life. The half-lives of radioactive atoms have a huge range; from nearly instantaneous to far longer than the age of the universe.
The decaying nucleus is called the parent radionuclide (or parent radioisotope), and the process produces at least one daughter nuclide. Except for gamma decay or internal conversion from a nuclear excited state, the decay is a nuclear transmutation resulting in a daughter containing a different number of protons or neutrons (or both). When the number of protons changes, an atom of a different chemical element is created.

Alpha decay occurs when the nucleus ejects an alpha particle (helium nucleus).
Beta decay occurs in two ways;
(i) beta-minus decay, when the nucleus emits an electron and an antineutrino in a process that changes a neutron to a proton.
(ii) beta-plus decay, when the nucleus emits a positron and a neutrino in a process that changes a proton to a neutron, also known as positron emission.
In gamma decay a radioactive nucleus first decays by the emission of an alpha or beta particle. The daughter nucleus that results is usually left in an excited state and it can decay to a lower energy state by emitting a gamma ray photon.
In neutron emission, extremely neutron-rich nuclei, formed due to other types of decay or after many successive neutron captures, occasionally lose energy by way of neutron emission, resulting in a change from one isotope to another of the same element.
In electron capture, the nucleus may capture an orbiting electron, causing a proton to convert into a neutron in a process called electron capture. A neutrino and a gamma ray are subsequently emitted.
In cluster decay and nuclear fission, a nucleus heavier than an alpha particle is emitted.By contrast, there are radioactive decay processes that do not result in a nuclear transmutation. The energy of an excited nucleus may be emitted as a gamma ray in a process called gamma decay, or that energy may be lost when the nucleus interacts with an orbital electron causing its ejection from the atom, in a process called internal conversion. Another type of radioactive decay results in products that vary, appearing as two or more "fragments" of the original nucleus with a range of possible masses. This decay, called spontaneous fission, happens when a large unstable nucleus spontaneously splits into two (or occasionally three) smaller daughter nuclei, and generally leads to the emission of gamma rays, neutrons, or other particles from those products.
In contrast, decay products from a nucleus with spin may be distributed non-isotropically with respect to that spin direction. Either because of an external influence such as an electromagnetic field, or because the nucleus was produced in a dynamic process that constrained the direction of its spin, the anisotropy may be detectable. Such a parent process could be a previous decay, or a nuclear reaction.For a summary table showing the number of stable and radioactive nuclides in each category, see radionuclide. There are 28 naturally occurring chemical elements on Earth that are radioactive, consisting of 34 radionuclides (6 elements have 2 different radionuclides) that date before the time of formation of the Solar System. These 34 are known as primordial nuclides. Well-known examples are uranium and thorium, but also included are naturally occurring long-lived radioisotopes, such as potassium-40.
Another 50 or so shorter-lived radionuclides, such as radium-226 and radon-222, found on Earth, are the products of decay chains that began with the primordial nuclides, or are the product of ongoing cosmogenic processes, such as the production of carbon-14 from nitrogen-14 in the atmosphere by cosmic rays. Radionuclides may also be produced artificially in particle accelerators or nuclear reactors, resulting in 650 of these with half-lives of over an hour, and several thousand more with even shorter half-lives. (See List of nuclides for a list of these sorted by half-life.)

View More On Wikipedia.org
  1. S

    Slope of N - t graph of radioactive decay

    I am not really sure how to interpret the slope. The equation is: $$N=N_o e^{-\lambda t}$$ If the graph is N against t, then what is the slope? I can find the slope if the graph is log: $$log N=log N_o -\lambda t$$ So if the graph is log N against t, then the slope is ##-\lambda## But if...
  2. G

    I What radioactive metal glows white hot all the time?

    1961 My father worked for a well drilling company called, Schlumberger in Lansing MI. One day he told me the company has a radioactive piece of metal that glows white hot all the time we keep it in a cement box in the ground inside a metal box with a lid. Sunday Schlumberger was closed and no...
  3. eneacasucci

    I Q value for a radioactive decay

    The Q value for a reaction is the amount of energy absorbed or released during the nuclear reaction. Is it correct to say that for a radioactive decay, since it is a spontaneous process, to occur the Q-value must be Q>0?
  4. L

    Are spent nuclear fuel rods radioactive?

    Are spent fuel rods radioactive and are the spent fuel rods cooling pools discharging radioactive water (tritium) into the environment?
  5. C

    The percentage error in the Radioactive substance Population

    Please check the question below as given originally. Answer given is 25%. I am unable to proceed. It is given that the half-life is underestimated by 10% therefore it must be larger than originally estimated. What I can find using the percentage error formula is ##\left(...
  6. S

    What causes the radioactive decay of an unstable nucleus?

    A philosopher whose work I'm using in a paper uses a radium atom's decay as an example of a "spontaneous power," or an uncaused event. My professor, though, says "quantum fluctuations" cause radioactive decay. What are these fluctuations, and do we know what causes them? It's a college paper, so...
  7. Kairos

    I Twin Paradox with radioactive twins

    Replace the twins in the twin experiment by identical radioactive samples containing the same starting number ## N_0 ## of atoms. One (A) stays on Earth while the other (B) makes a round trip at high speed. When back the traveling sample is more radioactive because its half-life ## \Delta t1/2...
  8. mesa

    Looking for a digital copy of the Table of Radioactive Isotopes

    Hello all, I am looking to get an electronic copy of the Table of Radioactive Isotopes by Edgardo Browne and Richard B. Firestone. I know that we can run software that incorporates this database here: https://www2.lbl.gov/LBL-Programs/Gamquest.html , but I am looking for an electronic copy to...
  9. Tristan_Ruel

    I Help getting my Cloud Chamber to work please

    Hello! I'm currently building a cloud chamber, my end goal is to make it powered by Peltier chips but that won't happen until I can make it work with dry ice. I've been able to achieve a supersaturated layer of isopropyl alcohol in the chamber, however, even with very radioactive uranite...
  10. A

    I Radioactive Dating of Asteroid Elements: How Do Scientists Know?

    When scientists use radioactive dating of elements in the asteroids to determine the age of the solar system, how do they know what the original amount of the radioactive element that was in the rock was? Do they need to know what the original amount of the radioactive element was in the rock...
  11. entropy1

    I Schrödinger's Cat and radioactive atom

    Particles can be made to be in superposition of their states. Concerning Schrödingers cat, if the cat is in superposition of being dead and alive, does that mean that the atom that drives the narcotic is in superposition of having decayed and not having decayed? And does that mean that any...
  12. Mayhem

    Chemical inhibitions of radioactive elements

    Is it possible to chemically inhibit (block/absorb) ionizing radiation from radioactive elements, and is any research being done in this area to use it for long term storage of nuclear waste (in conjunction with other precautions, of course)?
  13. CPW

    B Shorter half-life and therefore very radioactive -- why?

    In reading through The Physics of Energy, the textbook describes the decay chain of U-238: "The longest half-life of any descendent in the chain is less 1 million years. Many half-lives are much shorter, making those nuclides very radioactive." Why does having a short half-life make a...
  14. P

    I Radioactive decay question for K --> Ca

    As I understand 40K decays into 40Ca over a period of ##1.248(3)×10^9## yrs. Assuming this is the natural rate of decay, is there any way to shorten the period of decay (increase the rate of decay), for example, under extreme pressure or heat? Thanks:biggrin:
  15. J

    Are fluorescent dyes radioactive?

    I noticed the construction workers and gardeners and road construction workers wear neon green vests that look fluorescent, how are the dyes for those clothing made? Are they radioactive?
  16. J

    Is my used Geiger counter radioactive?

    I’m a mom and was worried about radiation in the new house we moved into, so I ordered a Geiger counter (the GQ gmc 500 plus) on amazon. But I noticed the screen protector film wasn’t pressed on all the way so there were some bubbles, there also was one scratch on the screen protector film and...
  17. BWV

    I How do hidden variables supposedly explain radioactive decay?

    If individual atoms are indistinguishable from one another, then how can you tell if atom A will experience radioactive decay before identical atom B? ISTM there would have to be some underlying structure beyond electrons and quarks and unique to each atom / particle to be able to do this...

    Poisson's Distribution application in Radioactive decay

    Summary:: I have been provided with the table in which N and occurence are given. I have been asked to calculate the 1. Total count 2. mean count 3. mean count. Now, assuming our distribution described by Poisson's we need to calculate the tasks. The Poisson's distribution is given by...
  19. dRic2

    How to measure the activity of a radioactive source

    Hi, I've been reading about radiation detectors (manly form Knoll's book), but there is something I don't understand. Radiation detectors are of very different nature, but they all share a common process to detect a type of radiation: - I have a control volume - The incoming radiation interacts...
  20. Dukon

    A What is the cause of radioactive decay?

    A prior closed post inquired as to precisely what determines the time of any given decay. I wasn't able to comment during that thread, but most responses were about probability and other aspects of the problem. I did not see however any mention of quantum fluctuations as possibly participating...
  21. D

    B Exact cause of radioactive decay?

    I recognize that radioactive decay is a spontaneous process in which an unstable atomic nucleus breaks into smaller, more stable fragments, but exactly what is it that causes an atom to decay at a particular time rather than at some other time?
  22. P

    Calcualtion of electric potential and radioactive decay

    This is just a representative diagram to visualize Surely a very tough one for me to solve. The number of nickel atoms are not mentioned. if the number of decays are ##3.78∗10^8## and with each decay depositing 100keV. The total energy deposited is ##100keV∗3.78∗10^8=6.048∗10^6## I have to...
  23. pimpypot

    Wood/Glass/Metal Where to Find Uranium Glass Beads/Wands & Safety Protocols

    I cannot find a source of uranium glass beads/wands for art making. It is mentioned online that one can make UV glass with a derivative of uranyl nitrate, UO2(NO3)2 . Does anyone know a source of uranyl nitrate, or raw glass material, and what are the minimum safety protocols, such as...
  24. C

    B Is glow in the dark shirt radioactive?

    You have seen shirts with figures or drawings that glow in the dark at night. Is it composed of radium ink? Are there radium ink being used now or are all glow in the dark ink safe?
  25. N

    Does radioactive decay exhibit stimulated emission?

    If you have a lump of the same species of radioactive isotopes, why can't the photons emitted from the radioactive decay of one nucleus cause spontaneous emission from other atoms? I presume it doesn't, because if it did, there would be a geometric effect of radioactive decay, which is not...
  26. B

    Why didn't radioactive decay probabilities cause the same uproar as QM

    It is equally puzzling why we are confined to probability amplitudes for RD as in QM measurements. Newtonian determinism is undermined in both, so why were there still Newtonian determinists around when QM hit the scene? We still have deterministic equations for both ofc but they are limited to...
  27. D

    B Is Radioactive Decay Uncaused/Causeless?

    I know that it has a cause! It happens to make the nucleus more stable. But some say it has no cause. I am confused actually.
  28. A

    I Nuclear Fusion: Radioactive Decay?

    Radioactive decay modes always release energy; but why can't nuclear fusion of light elements be a mode of radioactive decay? I guess because although such processes are exothermic, we need an inaccessible fairly high amount of energy to overcome the electrostatic repulsion barrier. But now...
  29. A

    B Input Energy of Radioactive Decays

    But how about some radioactive decays? (α, SF, CD, ...) Don't we need energy to to separate some nucleons of a radioactive nucleus?
  30. A

    B Radioactive decay, Stability and Halflife

    As it's written in the following article, nuclear binding energy is always a positive number; thus it takes energy to disassemble a nucleus into its nucleons. ...The binding energy is always a positive number, as we need to spend energy in moving these nucleons, attracted to each other by the...
  31. dRic2

    B Thought experiment -- A radioactive decay detector and randomness

    Take one radioactive element and put a detector all around it so that you can immediately detect whenever it will undergo radioactive decay. Have a clock connected to the detector to note the "exact" instant at which the atom decays. Let's say that after 3min after the clock started counting the...
  32. HotFurnace

    B Effects of Cooling and Heating in a Cloud Chamber

    Good day everybody! As we have already known the structure and operation of the cloud chamber, can someone explain to me why the cooling is done at the bottom of the chamber and the heating at the top, but not vise versa?? How this affect the function of the cloud chamber?
  33. R

    Physics question about half life / radioactive decay

    Homework Statement You have 0.0625 grams of an unstable element and 0.9375 grams of the stable daughter product. How many half-lives has it undergone? Homework Equations N=No (1/2)^(t/(t1/2)) In which N represents the final activity for a period of time No is the original activity t...
  34. J

    Vector Plasma vs. Variable Radioactive Decay

    Could there be a connection between Robert Zimmermann's work (McMaster Univ. Toronto) on Vector Plasma, and Jenkins and Fischbach's (Perdue Univ.) work on variations in the rate of radioactive decay for elements on Earth in relation to solar activity? Only looking for a confirmation that their...
  35. JesW87

    B Is radioactive decay truly random?

    Before you report this, yes I do know there was already another post like this one, but I don't feel like it fully answered the question. Note that I really don't know anything about quantum anything, but I'm trying to do some reading up on "randomness" and the consensus seems to be that this...
  36. A

    MHB Calculating New Emission Rate of Radioactive Source

    A radioactive source emits particles at an average rate of 1 pe second. Assume that the number of emissions follows a Poisson distribution. The emission rate changes such that the probability of 0 or 1 emission in 4 seconds becomes 0.8. What is the new rate? Thanks.
  37. HotFurnace

    How Does Radioactive Decay Affect Current in a Spherical Capacitor Circuit?

    Homework Statement A Metallic sphere with radius r=10cm is surrounded by a spherical metallic shell of radius 2r=20cm. The space exist between the two is vacuum. An amount of k=0.01 mol of radioactive 242Cm is strayed uniformly on the sphere, the radioactive isotope emit alpha particles which...
  38. A

    B Radioactive decay characteristics as measured by a dosimeter

    If I put a dosimeter 1 meter away from a gamma sample that starts decaying at the moment I switch on the dosimeter then how would I measure the dose level received by the dosimeter, would it gradually decrease over the first half life or would it stay the same throughout the first half life...
  39. S

    B Is Radioactive Decay Truly Random?

    How can radioactive decay be random if we can calculate aproximately when it will happen . For example we know that an isotope will decay every 2 years by calculating the half life . Doesnt that mean that the decay is systematic rather than random because we can calculate when its guna happen ...
  40. Krushnaraj Pandya

    Radioactive Decay Rates and the Relationship between Decay Constants

    Homework Statement Consider nucleus A decaying to B with decay constant D1, B decays to either X or Y (decay constants D2 and D3). at t=0, number of nuclei of A,B,X and Y are J,J,0 and 0. and N1,N2,N3 and N4 are the number of nuclei of A,B,X and Y at any instant. My question is, what is the...
  41. Hercuflea

    Half life from two identical radioactive sources cpm

    Homework Statement " Independent measurements are taken on two identical radioactive samples. On the first radioactive sample, a radiation detection system measures N decays on a radioactive sample during a total period of T. On the second radioactive sample, a radiation detection system...
  42. C

    I Activity of daugther isotope in secular equilibrium

    Consider chain of two radioactive decays ##A \to B\to C##. The equation that regulates ##N_B## is $${\frac {\mathrm {d} N_{B}}{\mathrm {d} t}}=-\lambda _{B}N_{B}+\lambda _{A}N_{A}$$ I can't understand why the activity of ##B## is get as ##\lambda_B N_B##, for example at page 20 here...
  43. T

    I Radioactive decays, different modes share

    Hello, I'd like someone to help me understand, how can I tell from available data, what is the approximate share of different decay modes, for some given nuclide activity. Let's take 90Y for instance. It's known for being beta-emitter, but it emits gammas and X-rays as well. How to...
  44. Muhammad Danish

    Can a Gold Leaf Electroscope Detect Alpha Particles?

    Can we use Gold Leaf Electroscope to check whether a radioactive material gives off Alpha particles?
  45. C

    I Why is radioactive decay so rare?

    Hi all, I'm just curious about the weak force and how it works. If quarks and electrons both have weak iso-spin and are constantly whizzing about next to their neighbour's (especially so inside a nucleon), what prevents say, the up quarks from emitting a W- boson everytime they are near a down...
  46. Ilya Furman

    How Much Heat is Produced by Radioactive Waste?

    To begin, I am not sure whether or not this is the correct location for this post since I am a complete greenhorn to this forum (just joined today!). I ask how much heat is produced by radioactive waste because I was wondering if it was viable to reuse all the tons of stored radioactive waste...
  47. H

    [Poisson Stats] Error on half-life for radioactive decay

    Hi there, not sure whether this is in the right section but: I've made two runs of a radioactive decay experiment where I've got a log(N) vs. time plots. From this I've got the decay constants and hence the half-life. I've averaged these two half-lives ( = 160 secs) and now I'm trying to work...