Radioactivity(Half-Life):Types & 5 Important Facts

Half-life Definition:

“Half-life is defined by the interval of time required for an atom to reach 1/2 of the atomic nuclei of a radioactive sample to decay from original mass”.


Radioactivity is the spontaneous emission of radiation, in the form of different particles (alpha and beta ) or as photon in subsequent to a nuclear reactions.

In the year 1896, Famous French physicist Henri Becquerel discovered spontaneous radioactivity.  This is one of the most well-known accidental and important discoveries in the history of science. This has started multiple direction of research field and has great impact on modern science and technology.

3 most common types of radiation are:

  • Alpha.
  • Beta.
  • Gamma.

Explanation of half life:

image 15
Image Credit: OpenStax, CNX Chem 21 03 HalfLifeCC BY 4.0

Formula of half life:



  • N0 is the initial quantity.
  • N(t) is the quantity that present after t sec.
  • t1⁄2 is the half life.
  • τ mean lifetime (+ve),
  • λ decay constant (+ ve).

The three parameters 1 ⁄ 2, τ, and λ are all directly related in the following way

{\displaystyle t_{1/2}={\frac {\ln(2)}{\lambda }}=\tau \ln(2)}

Stability of Isotope’s half-lives:

Isotope half-lives:
Isotope half-life: The darker more stable isotope region advances from the line of protons (Z) = neutrons (N), as the element number Z turn out to be larger.

Half life of Elements in Periodic Table and their Stability:

1280px Periodic Table Radioactivity.svg
Periodic table
Sky Blue: these Elements that comprise at least 1-stable-isotope. Green: To some extent Radioactive elements: the most stable isotope is very high half-life in the range of few million years. Yellow: Significantly Radioactive element: the most-stable isotopes have halflife ranges in-between 1000 and 35000 yrs. Orange: Radioactive element having half-life in-between one day and 130 yrs. Red: Highly radioactive element: half-life between more than a few minutes to day may be. Violet: Extremely radioactive element and its half-life is in the range of less than several minutes. Very less study has been their about these element due to their high risk level radioactivity.

Image Credit: Periodic_Table_Armtuk3.svgArmtuk (talk) derivative work: Alessio Rolleri (talk) derivative work: Gringer (talk), Periodic Table RadioactivityCC BY-SA 3.0

Measurement of Radio Activity using Radiation Detector:

Radiation Detector:

“A device for measuring nuclear, electromagnetic or light radiation, generally detects nuclear radiation by determining the emission of ionizing radiation of alpha, beta particle and gamma ray.“

Dosimeter , Radiation Detector
Dosimeter , Radiation Detector image credit : pixabay free images

What are the three major types of radiation detectors?

The radiation detection instruments are simply detectors employed to measure the different type of radiation such as alpha, beta and gamma etc.
3 types of detectors frequently used, depending on the specific requirements of the device applications.

  • Gas-Filled Detectors
  • Scintillator Detectors
  • Solid State detectors.

What materials can block radiation?

Shielding: the metal like lead, tin and material like concrete, asbestos are good shielded material in addition to these normal water also utilized for protecting from the radiation exposure such as gamma rays and neutrons. This is main reason that most of the radioactive material stored in under water/concrete/lead shielded area, and this is the reason that dentist usually place a lead blanket to protect him and patient from the exposure of x-ray radiation.

Non-lead shield material is prepared with various chemical additives. Then it is mixed with the heavy metals for better attenuation. These may be used as shielding purpose like other good shielding material to absorb or to block radiation exposure. These metals may include tin, antimony, tungsten, bismuth or other heavy metals.

Biological half-life | Pharmacological half-life | Elimination half-life

“This is the time it requires from its maximum concentration (Cmax) to half-maximum concentration in human body.”

Note: This is different quantity than a normal radioactive half-life generally used in biological applications.

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