An overview of the half-life concept

Introduction to half-life

In radioactivity, half-life refers to the time needed by one-half of a radioactive atom’s nuclei to decay or degenerate into some other nuclear species or another element by emitting energy and particles. We can also define the half-life as the time taking to reduce the material to half of its initial value


Suppose we have Cobalt-60 which is a very common and popular radioactive element. The half-life of Cobalt-60 is 5.26 years. Thus, if you possess eight grams of Cobalt-60 at this time, its mass would get reduced to four grams after 5.26 years from now. It means the amount of radiation your eight grams of Cobalt-60 block is emitting right at this time would also be reduced to half. 

After another period of 5.26 years, its mass will also reduce to half and contains only two grams of Cobalt-60. Thus, you will not observe any visible change in mass or volume of the original sample after the passing of one or two half-life periods. The reason behind this unaltered mass and volume is that the mass of cobalt-60 has not just faded away, instead, its unstable, radioactive nuclei have gone converted into stable nuclei of nickel-60. Since both these stable and unstable nuclei are still together, the total mass of the sample is still the same. 

How does an atom disintegrate into another one?

The half-life phenomenon is expressing by almost all the unstable and radioactive atomic nuclei. However, every unstable nucleus possesses a particular way to decay into a stable one. The common ways by which an atom decays are alpha decay, beta decay, and gamma decay. Gamma decay is much faster than both alpha and beta ones. 

The efficiency of a decay method is usually calculate by measuring its decay range. We can find this by using half life calculator with steps. For example, the half-life for alpha decay ranges above one millionth per second. However, beta decay is one hundredth per second. The half-life of the gamma decay range is much shorter to even measure and it’s around 10-14 per second. 

Importance of half-life 

Safety and medical uses

The half-life helps scientists to predict the decay rate of a specific radioactive isotope to determine when one atom of that isotope will decay. By knowing about the half-life of an unstable atom, you can predict when a radioactive material should and shouldn’t be in hand. 

The thumb of the rule here is that a radioactive sample is completely safe to handle when it starts to emit radiation to that lower extent so they are not even able to detect it. Usually, it takes ten half-lives for radioactive material to reach that point of safety. 

It means if we inject radioactive I-131 into a human body to cure goitre disorder, its effect would last for ten half-lives that is equal to nearly eighty days.

Knowing the half-life of medical traces is important to clinicians since it should be long enough to cure the disorders and short enough not to damage healthy organs or cells. 

Related: Since the composition of any element will matter in a certain decay. If we have one atom of carbon it will diffuse with a different half-life period than two elements of carbon. For such purposes, you can also go through the composition calculator.

Carbon or radioactive dating

Radioactive dating is based on the same phenomenon of half-life and is quite helpful for determining the age of old things. The general rule of radioactive dating is to determine the amount of carbon-14 in the object. Carbon-14 is abundant in the cosmic layer of the atmosphere and there’s only a very minute amount of carbon-14 present in the biosphere. 

Mostly the carbon present around us is present in the form of carbon dioxide. Since plants only take the C-14, it becomes a part of their cellular structures and metabolism. These plants are then consumed by animals thus, the same amount of C-14 is transferred to them. In this way, the amount of C-14 remains the same in a living body. However, when a plant or any other living organism dies, the concentration of C-14 in its body drops. Since palaeontologists are aware of the half-life of carbon-14, which is 5730 years.

They easily figure out how much time ago an organism died. 

Carbon dating can only help to figure out the age of a thing. It can never be used to calculate the age of a meteor or a moon rock. To determine the age of non-living materials, scientists use potassium-40 or other radioactive isotopes. 

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