Radioactive decay refers to atomic nucleus that breakdown and change without warning. But what does that mean exactly?

    Below we've included comprehensive guide to understanding radioactive decay.

    If you need to convert units, like the becquerel or the curie, try this free calculator for quick and accurate conversions.


    What is radioactive decay?

    Everything in nature tends to crave stability or equilibrium as scientists tend to call it.

    When something goes out of balance, it compensates for the loss by changing normal characteristics.

    When this happens within atomic nuclei, we refer to it as radioactive decay and can measure this process by dating it.

    In other words, radioactive decay is the breakdown of an atom's nucleus that results in the release of energy in the form of ionizing radiation.

    What is the standard unit of radioactive decay?

    Today, the becquerel (Bq) serves as the standard unit, which measures the number of decays per second.

    One becquerel is equal to one radioactive decay per second

    However, a longer used unit is the curie, which specifically correlates with one gram of radium-226.

    How do you convert to other units?

    In order to convert any units of measurement, you need to think of them in terms of a numerical value.

    Remember, you need to change the scale you are measuring with, but not the actual measurement.

    When we are talking numbers that are extremely large or extremely small, scientific notion proves useful, and we need to put each unit into the same perspective.

    Conversion Factors

    1 becquerel = 1 radioactive decay per second. We also know that 1 curie = 3.7 x 1010 radioactive decays per second.

    Curie (Ci) to Bequerel (Bq)

    When converting curie to bequerel, add your variables to this equation:

    Bq = Ci x (3.7 x 1010)

    It's saying that 1 curie is equivalent to 3.7 x 1010 bequerel.

    Bequerel (Bq) to Curie (Ci)

    To convert a measurement in bequerel into a measurement in curie, you'll use this formula:

    Ci = Bq x (2.7 x 10-11)

    This is saying that one bequerel equals 2.7 x 10-11 curie.

    For a simpler way to convert or to check your own math, use an online radioactive decay converter.

    How does radioactive decay happen?

    The process occurs:

    • spontaneously, meaning without a reaction with any other particle
    • stochastic, meaning randomly
    • unpredictably, but with the Law of Large Numbers, we can predict it with a large number of identical atoms in a collection

    This happens when an unstable nucleus does not possess enough binding energy to keep it all together, meaning, the strong force loses out, creating an isotope.

    The isotope wants stability, so it throws off protons, neutrons, or other forms of energy until it finds balance.


    Let's look at carbon on the elemental table. A typical, stable carbon atom contains 6 of each, protons, neutrons, and electrons.

    However, if we look at an unstable atom, like carbon 14, we see the atomic mass is 14 rather than 12 because it contains two additional neutrons.

    These two additional neutrons throw off the particle's balance, which provides the strong force and so, carbon 14 throws off those extra neutrons, thus emitting ionizing radiation.

    Are there different types of radioactive decay?

    Yes, there are three main types of radiation decay.

    1. Alpha Decay

    Alpha decay occurs with the nuclear breakdown of heavy and transuranic elements emits alpha particles.

    What Is an Alpha Particle?

    An alpha particle consists of four tightly bound protons and neutrons, two of each, making them identical to a helium atom.

    They move incredibly slowly, in terms of particles, at speeds of 20,000,000 meters per second.

    Which Elements Can Produce These Particles?

    Alpha particle producers include:

    • thorium
    • uranium
    • radium
    • actinium

    When these elements decay, they set off ionizing radiation into the environment.

    Are They Harmful When Released?

    Because of the elements' large masses, these particles move slowly through the air and collide with other particles along the way that pull electrons away from the particles, making them highly ionizing.

    This makes them fairly safe.

    In fact, your clothing and skin will stop them from harming you.

    Unless they occur inside the body or enter the body through a wound, the corner of their eye, or the lungs, quick exposure will not harm you.

    Is Alpha Decay Useful?

    Yes, we can use alpha decay to our benefit!

    Smoke detectors utilize alpha radiation to detect fire; smoke consumes the alpha particles causing the alarm to sound.

    2. Beta Decay

    When either a proton turns neutral, or a neutron gains a positive charge within a nucleus that has too many protons or neutrons.

    This change happens via one of three methods:

    • proton decay
    • neutron decay
    • electron capture

    This emits beta particles and beta decay occurs.

    What Is a Beta Particle?

    A beta particle is a single, fast-moving electron, that ejects from an unstable nucleus, despite the fact that electrons do not even live in the nucleus, but in shells surrounding it.

    Two types exist. Negative beta decay occurs from the regular neutron emission.

    A positron emission occurs with a positively charged electron.

    These particles weigh significantly less than their positive counterparts, protons.

    What Produces Beta Radiation?

    This happens in one of two ways:

    • naturally after one or more alpha decay occurs in a chain
    • in nuclear fission byproducts.

    The nature of production puts these particles into a separate category than alpha particles.

    Are They Harmful?

    Yes, because they move extremely fast and therefore and are less ionizing than alpha particles.

    So, they travel further through the air and deeper through layers of clothing and skin, causing bad burns to exposed areas.

    Can We Use This?

    Though these particles can harm us, they can also heal us.

    An incredibly important use of beta radiation is in the treatment of certain cancers, like bone, since it can penetrate the skin deeply.

    The same particles that cause burns on our body, attack the cancer cells and kill them when the specialist targets them.

    3. Gamma Decay

    Also commonly called gamma emission, the spontaneous process generally follows the beta decay and occurs due to an unstable nucleus depleting the extra energy through an electromagnetic process.

    This results in a gamma ray.

    What Is a Gamma Ray?

    Super energetic photons made up of electromagnetic energy, create a gamma ray.

    Considering all the products of radioactive decay, gamma rays possess the highest energy and shortest wavelength.

    Are They Harmful?

    Extremely, due to their supercharged nature. Not only can gamma rays pass through skin, but they pass through lead with ease.

    They alter the genetic makeup of the body, making exposed persons extremely ill and causing life threatening effects, among other problems.

    Can We Harness Their Power for Good?

    Yes, they prove useful when harnessed with extreme caution. Some uses include:

    • investigating oil wells deep beneath the ground
    • sterilizing surgical equipment
    • imaging internal organs and blood flow for special testing
    • gauging aircraft fuel

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