Radioactive Decay

Also known as nuclear decay, radioactive decay is the decrease of radiation through time.

1,734 Questions
Radioactive Decay

What is radioactive decay?

Radioactive decay is the spontaneous change or disintegration of an unstable atomic nucleus as it transforms itself to lose energy. It does this by the release of either particulate radiation or electromagnetic radiation, or both. This atomic event is random and cannot be predicted, but by applying statistical principles to large numbers of a given radionuclide, an "average" decay time can be found, and we have the half-life. There are several different types of radioactive decay. They range from spontaneous fission to alpha decay, beta decay and a couple of others.

The spontaneous breakdown of a nucleus

Electromagnetic Radiation
Radioactive Decay

What can happen if you are exposed to large amounts of radiation?

The answer to this question varies dramatically depending on the TYPE of radiation involved, as there are many; as well as how the "large amounts of radiation" are received.


First there are two different main types of radiation, and within each type there are different subtypes, each having differing effects in overdose:

  1. Electromagnetic radiation - e.g. radio, TV, microwave, infrared, light, ultraviolet, x-ray, gamma ray.
  2. Particulate radiation - e.g. alpha, beta, gamma, neutron, cosmic ray, heavy ion.

Note: The gamma ray listed as electromagnetic radiation and gamma listed under particulate radiation are the same radiation, but at that very high energy per photon particle quantum mechanics makes it impossible to clearly say it is either an electromagnetic wave or a particle.


The effects of overdose exposure of each of the above listed types of radiation are:

  • radio - very difficult to impossible to overdose
  • TV - very difficult to impossible to overdose
  • microwave - you get cooked inside, this is called "deep tissue burns" and can be instantly fatal in some cases
  • infrared - thermal skin burns
  • light - very difficult to impossible to overdose, except directly to the eyes which produces temporary blindness
  • ultraviolet - sunburn, exposure to the eye will cause permanent blindness
  • x-ray - radiation sickness/poisoning
  • alpha (external exposure) - intact skin shields 100% of alpha particle radiation, impossible to overdose
  • alpha (internal exposure) - cancer
  • beta - beta burns, on skin resembles a very very bad sunburn (but may be in small dots around the points of contact with beta emitting fallout grains), internally it is usually fatal as it causes massive tissue death
  • gamma - radiation sickness/poisoning
  • neutron - radiation sickness/poisoning, also will make you radioactive (no other type of radiation will do this)
  • cosmic ray - on the surface of earth the atmosphere is such a good shield that it is impossible to overdose, but in space radiation sickness/poisoning are possible
  • heavy ion - tends to be shielded effectively by skin, but at high enough energies will cause radiation sickness/poisoning

The symptoms of radiation sickness/poisoning are nausea, vomiting, diarrhea, hair loss, etc. but in extremely high overdose it kills the nervous system causing very sudden death. The insidious thing about radiation sickness/poisoning is that just as the patient begins to appear to improve, the immune system fails and massive infections set in, which kill many.

Radioactive Decay

What is the probabilistic nature of nuclear decay?

Nuclear decay is a quantum mechanical process, mediated by the weak and strong nuclear forces. All quantum mechanical processes are probabilistic, not deterministic.

Radioactive Decay

What type of nuclear decay releases energy but not a particles?

All nuclear decay releases both energy and particles. Even gamma rays from the meta stable decay of Technetium-99m, being only photons, are particles, because a photon is considered a particle - or is it energy? - or is it mass? - hmmm? - see quantum mechanics on that one.

Also, Einsten's famous mass energy equivalence equation e = mc2 states rather plainly that energy is mass and mass is energy. That means that if nuclear decay releases energy, then it also releases mass, and vice versa. There is no way around the equivalence.

Do not misunderstand this. The equation does not mean that energy can be converted into mass or vice versa, it means that energy is mass and vice versa. Neither energy nor mass can be created nor destroyed. So, when an atomic bomb goes off and loses mass generating a high amount of energy, the mass that is lost is simply carried away with the energy.

Sorry if it seems I deviated from the topic, but I did not. This is part of reinforcing the answer and enhancing the explanation.

Radioactive Decay

What is the nuclear decay equation for americium-244?

The equation for the beta decay of 244Am is:

95244Am --> 96244Cm + -10e

with -10e representing the beta particle or electron.

Radioactive Decay

What do scientists use to date the exact age of fossils?


Radioactive Decay

What is radioactive decay used for?

it is used by scientist to to calculate a rock's age

Radioactive Decay

Is the weak nuclear force associated with nuclear decay?

(Warning: This is a little long. For a summary, scroll down to the bottom.)

Depends on the kind of decay. There are many different types of possible nuclear decays:

  • Alpha decay (throwing off helium-4 nuclei)
  • Beta-minus decay (converting neutrons to protons, releasing electrons)
  • Beta-plus decay (converting protons to neutrons, releasing positrons)
  • Gamma decay (emission of high-energy photons after alpha or beta decay)
  • Electron capture (an electron falls into the nucleus, converting protons to neutrons without releasing positrons)
  • Spontaneous fission (the nucleus suddenly splits in two)
  • Proton decay (a lone proton is thrown off)
  • Neutron decay (a lone neutron is thrown off)9

Of all of those decays, beta decays and electron capture involve the weak nuclear force.

Deep inside of a proton or neutron, there are 3 fundamental particles named "quarks". In atomic nuclei, there are two kinds of quark: up and down. Up quarks have a charge of +2/3, while down quarks have a charge of -1/3 (yes, quarks have fractional charges.) Because of the strong nuclear force, quarks must gather into groups of 3.

A proton contains two up quarks and one down quark. Two up quarks (charge +4/3) and one down quark (charge -1/3) add up to the proton's net positive charge of +3/3.

A neutron contains two down quarks and one up quark. We'll let you do the math on this one, but they ultimately balance out to 0. Neutrons are heavier than protons, and, given the opportunity, they will spontaneously transform into a proton, throwing off an electron to balance the charges. A mysterious particle called an "antineutrino" is emitted (more on antineutrinoes later). This is caused by a down quark turning into an up quark via the weak nuclear force.

Beta-minus decay is simply when a neutron in a nucleus is converted into a proton, throwing off a high-energy electron. This electron is our beta-minus particle.

Beta-plus decay does not normally occur, because protons are lighter than neutrons, so they should not decay. But, in some particularly light nuclei, e.g. carbon-11, there is enough energy for a proton to transform into a neutron. This produces a high-energy particle called a positron. Positrons are basically electrons with a positive charge, instead of a negative one. A neutrino is also produced, more on these later. This is also governed by the weak nuclear force.

Electron-capture occurs in the same nuclei beta-plus decay can take place in. We'll use potassium-40 as our example. K-40 can either undergo beta-plus decay, or, there is a slighter chance one of its protons will "capture", or consume, one of its electrons. This converts the electron into a neutrino, while satisfying the nucleus, which transformed from potassium-40 into stable argon-40.

Neutrinoes are very evasive particles. They do not interact electromagnetically, hence the name, which means "small neutral one" in Italian. They are almost massless, and for a while, it was believed they were. Neutrinoes were first theorized in 1930 to explain why beta particles often had different energies, but were only found in 1955. Neutrinoes only interact via the weak nuclear force. They mainly serve a purpose as satisying the balance. There are also antineutrinoes, which are almost identical to normal neutrinoes, except for their position on the balance, explained below.

This balance is of something called "electron number". You see, in a nuclear reaction, the total number of electrons involved must be conserved, both before and after the reaction. Electrons and neutrinoes have an electron number of +1. Positrons and antineutrinoes have an electron number of -1. In beta-minus decay, we start with a neutron (electron number 0). It turns into a proton (also electron number 0), producing an electron (electron number +1) to conserve charge. In order to satisfy the balance and conserve electron number, an antineutrino (electron number -1) is released. Neutrinoes have no electrical charge, so both charge and electron number are balanced.

Alpha decay, gamma decay, and spontaneous fission do not rely on the weak nuclear force. Alpha decay is when a helium nucleus manages to escape the nucleus. Proton and neutron decay work in similar manners. Gamma decay is when nucleons leaving produces holes in lower-energy states, which higher-energy nucleons move into, releasing the energy in a high-energy photon. Spontaneous fission also works similarly to alpha decay: in fact, alpha decay is a version of spontaneous fission!

So, to answer your question simply, some decays are associated with the weak force, some aren't. Depends on which decay you're talking about.

Radioactive Decay

What happens to an isotope during radioactive decay?

The decaying atom will emit something - which usually involves an alpha particle, a beta particle, a gamma ray, or some combination - and become a different type of atom.

Radioactive Decay

What is the nuclear decay equation for gamma?

Gamma is not a decay process. It is a consequence of a decay process, but it, in itself, is not a decay process. It is the emission of a photon from the excited state of the nucleus in response to a decay process such as alpha or beta that changes the nucleus and leaves it with excess energy.

Radioactive Decay

How are nuclear decay rates different from chemical reaction rates?

nuclear decay rates take more time and chemical reaction rates could happen fast.

Radioactive Decay

Radioactive decay can be affected by?

The rate of decay of a radioactive element cannot be influenced by any physical or chemical change. It is a rather constant phenomenon that appears to be independent of all others. The rate of decay is given by an element's half life, which is the amount of time for approximately half of the atoms to decay.

Radioactive Decay

What is radiocarbon dating or carbon-14 and how does it work?

Radiocarbon Dating
All organic matter contains carbon, which is an element. But there are different types of carbon, called isotopes. The most common isotope is carbon-12 (or 12C), which (according the article) makes up 98.89 percent of the naturally occurring carbon. There's carbon-13, or 13C, which is much rarer, accounting for only 1.11 percent, and then there's carbon-14, or 14C, which makes up a ridiculously tiny fraction of existing carbon. (The periodic table of the elements also reflects the existence of isotopes by showing a weighted average for the atomic weight of each element, but I digress.)

The first two isotopes, 12C and 13C, are stable, but 14C is unstable; that is, it's radioactive! So far, so good. Nothing hard to get your brain around. Living organic matter will have steady and predictable concentrations of each isotope of carbon, pretty much the percentages mentioned above. But dead stuff won't. After something dies, the 14C decays over time (because it is radioactive) and doesn't replenish as it would in a live specimen because the dead thing isn't eating and breathing or otherwise exchanging molecules with the outside world anymore). In other words, the amount of 14C in dead organic matter will grow smaller. And since scientists know exactly how long an amount of 14C takes to decay, they can compare the amount of 14C in a specimen to the amount of 14C a modern piece of organic matter and calculate the age of the specimen. Since it takes 5,568 years for an amount of 14C to decay by 50 percent (half), if a specimen has one half the amount of 14C as a modern piece of organic matter might have, we conclude it is about 5,568 years old.

Here's an analogy: Imagine you have a gallon of water to which you add one ounce of blue dye. And say that every 5,568 years you add another gallon of water to the mixture. Doing that basically cuts the concentration of blue dye in half. You then take a gallon of that diluted mixture and add another gallon of pure water to it 5,568 years later. The concentration of blue dye is cut in half again. Now imagine repeating this process for quite some time. If you take a sample of the diluted water and measure the concentration of blue dye, you will be able to determine how many dilutions took place, and since you know the dilutions happen every 5,568 years, you can estimate how old the sample is. See link below for more information.

Carbon-14 builds up in living tissue at a constant rate and starts to break down when the tissue dies. Scientists can measure the amount of carbon-14 in a piece of old wood for instance, and say that because there is only a certain amount left, the tree died 1000 years ago.
Nuclear Physics
Bombs and Explosive Materials
Radioactive Decay

When talking about the so called dirty bomb what are various kinds of weapons and how likely is it that terrorists will be able to obtain a weapon which will have a devastating impact?

A dirty bomb is an explosive device designed to eject or spray radioactive material over a small area. It does not produce mass amounts of fallout compared to a traditional nuclear device, since there is no fission involved. A conventional explosive such as those used on Oklahoma City, Beirut or the first World Trade Center attack, if packed with powdered or pelleted radioactive material (strontium, plutonium, etc.) would eject that material into buildings, parks, streets and people in the surrounding area. While the immediate death count would be low, many people would suffer from radiation sickness. Cleanup would be massively expensive and time-consuming. An area of several square miles would likely be uninhabitable for years.

Potential terrorists would buy the material on the black market from sources such as former Soviet Union countries, North Korea or the Middle East. Getting it refined in secret would be somewhat difficult. Transporting it to the target area would also be hard but not impossible.

*** I agree with the first part of the above answer, however anyone who is even fairly determined can get radioactive material. it is found is some medical equiptment, and other sources. The radio active material can be put in a regular pipe, or car bomb. If exploded in a populated area it would spread the radioactive materiel over a large area. Large numbers of people would have increased rates of cancer and other radation sicknesses. Other people would likely be injured by the direct blast and first responders would be in danger when going into rescue the wounded. The history (discovery, one of them) did a show on what would happen if a terrorist attacked with either a dirty bomb or a full atomic bomb. They did a good job and it is worth watching.

Nuclear Physics
Radioactive Decay

What is the decay products of uranium 238?

U-238 is the most abundant (99.3%) of the three naturally occurring isotopes of Uranium. The other two are U-235 and U-234.

U-238 decays spontaneously to Thorium-234 by alpha particle emission. This decays by beta decay to Protactinium-234 and then that undergoes beta decay to become U-234.

There are many more decay steps by alpha and beta emission. The end result is Lead-206 which is stable.

The full path can be found in the Argonne National Laboratories Human Health Fact Sheet, August 2005, titled Natural Decay Series: Uranium, Radium, and Thorium

This is found at:

Elements and Compounds
Radioactive Decay

Can carbon fourteen be used in dating organic substances from the Precambrian era?

No. C-14 dating is not effective for samples older than about 50,000 years.

Radioactive Decay

What is the daughter nucleus (nuclide) produced when 90Sr undergoes beta decay by emitting an electron?


Atoms and Atomic Structure
Radioactive Decay

What happens during radioactive decay?

An unstable nucleus loses particles until it becomes stable

Elements and Compounds
Radioactive Decay

What is Polonium used for?

It can be alloyed with beryllium to provide a source of neutrons. It can eliminate static charges in textile mills. It is used on brushes to clean film, and can provide thermoelectric power in space satellites. Of course, it can also be used as a poison, as it is over 250,000 times as toxic as cyanide, and is very hard to find in a body.

Radioactive Decay

Is anything better than carbon dating?

The bible! haha just joking.

Electromagnetic Radiation
Poisons and Toxins
Radioactive Decay

What will happen if radiation gets on your skin?

it depends. if it was a lot of radiation, it could burn your skin.


Radiation comes in multiple types from multiple sources. In fact, skin is our body's primary defense against the forms that we normally encounter every day from a variety of sources, including the sun, electronic devices, the earth itself, etc... If a person is exposed to certain kinds, in high enough doses, or for prolonged periods, it causes burns. A common example is a simple sunburn. In a less common example, this can cause severe burns, blisters and complete disintegration of the skin itself, not to mention the tissue underneath. A larger danger of widespread radiation exposure is to the environment itself, especially food and water, as this bypasses our skin, essentially cooking us from the inside out. This leads to a variety of medical problems including cancer and birth defects.

Radioactive Decay

What does Radioactive decay release?

Energy. Specifically in the form of 4He nuclei (alpha decay), electrons/positrons (beta decay), or high-energy photons (gamma decay)
alpha particles, beta particles, and gamma rays

Radioactive Decay

Can you use carbon dating on diamonds?

No. Carbon dating only works on organic matter.

Radioactive Decay

What is the nuclear decay equation for silicon-32?

The equation for the beta decay of 32Si is:

1432Si --> 1532P + -10e

where -10e represents a negative beta particle or electron.

Radioactive Decay

How does carbon dating work?

The ratio of carbon-12 and carbon-14 are constant in a living organism. However, no more carbon-14 is absorbed after the organism dies. The rate of decay of carbon-14 is known so this can be used to estimate the age of the organism.


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