In another article, we have learned that the elements that emit alpha, beta and gamma rays spontaneously are called radioactive elements. All elements are not radioactive elements. Again, all isotopes of an element are not radioactive. In this article, we are going to discuss which isotopes of radioactive elements have radioactivity property. Here, we will choose the examples of radioactive isotopes of most popular elements like hydrogen, carbon, oxygen, Nitrogen, Iodine, Potassium, uranium, etc.
Contents in this article:
- Radioactive elements
- Radioactivity of Isotopes
- Examples of Radioactive isotopes and their uses
What are Radioactive elements
Some of the elements in the periodic table can spontaneously emit radioactive radiations like alpha ray, gamma ray and beta ray. Such elements are the radioactive elements. Generally, heavier nucleus having atomic mass number greater than 200 (like Uranium, Thorium, Polonium, etc.) are the radioactive elements. But there are some radioactive isotopes of lighter elements too. Among the lighter elements hydrogen, carbon, oxygen, nitrogen, phosphorus, iodine, etc. have radioactive isotopes.
Radioactivity of Isotopes
Earlier I told that all the isotopes of lighter elements are not radioactive. But there may be some isotopes that shows radioactive property. For example, among the isotopes of carbon, only C-14 shows radioactivity, among the isotopes of hydrogen, only Tritium is radioactive. Again, multiple isotopes of an element can also be radioactive, but they will have different percentage of radioactive property.
Examples of Radioactive isotopes and their uses
Here we are going to discuss the examples and uses of radioactive isotopes of some popular elements like Hydrogen (H), Oxygen (O), Nitrogen (N), Potassium (P), Iodine (I) and Uranium (U). We have discussed radioactivity of elements one by one as below.
Radioactive isotopes of Hydrogen
Hydrogen atom has seven isotopes from 1H1 to 7H1. Among these isotopes only three isotopes are occurred naturally and rest are artificial isotopes having very small life-times. Natural isotopes of Hydrogen are Protium (1H1), Deuterium (2H1) and Tritium (3H1). Among these three natural isotopes Tritium is radioactive isotope that occurs naturally due to the interaction of cosmic rays with atmospheric gases. So, the radioactive isotope of hydrogen is Tritium. Tritium emits beta- rays and gets converted into Helium atom. Again, all the artificial isotopes of hydrogen are radioactive. All of these artificial isotopes decay to Tritium and then Tritium decays into Helium atom.
| Isotope of Carbon | Stability | Half-life | Decay | Daughter Isotope |
| Protium (1H1) | Stable | – | – | – |
| Deuterium (2H1) | Stable | – | – | – |
| Tritium (3H1) | Radioactive | 12.32 years | Beta– | 3He2 |
Tritium is used in thermonuclear fusion weapons.
Radioactive isotopes of Carbon
Carbon atom has 15 known isotopes including natural and artificial isotopes. These are from 8C6 to 22C6. Among these 15 isotopes, there are three natural isotopes – 12C, 13C and 14C. Among these natural isotopes 12C and 13C are stable isotopes and 14C is long-lived radioactive isotope with a half-life of 5730 years. 11C is the most stable and radioactive isotope from the group of artificial isotopes of carbon. All the artificial isotopes of carbon are radioactive isotopes, but their half-life are very very small. So, C-11, C-12, C-13 and C-14 are the important isotopes of carbon. C-11 emits beta+ rays and C-14 emits beta- rays.
| Isotope of Carbon | Stability | Half-life | Decay | Daughter Isotope |
| 11C6 | Radioactive | 20.36 min | Beta+ | 11B5 |
| 12C | Stable | – | – | – |
| 13C | Stable | – | – | – |
| 14C | Radioactive | 5730 Year | Beta– | 14N7 |
Use of Radioactive isotopes of carbon
- The radioactive natural isotope 14C is used to determine the age of old trees, statues, Fossils, rocks, etc. This is known as Carbon dating.
- Stable isotopes of carbon in CO2 are utilized by plants during the photosynthesis.
Radioactive isotopes of Oxygen
An Oxygen atom has total 16 isotopes from 11O8 to 26O8. Among these 16 isotopes only three are stable isotopes and other 13 are artificial radioisotopes. 16O8, 17O8 and 18O8 are the naturally occurred stable isotopes. These are not radioactive in nature. Among the radioactive isotopes of oxygen 15O8 is most stable with half-life of 122.24 seconds.
Radioisotopes of oxygen have not much uses.
Radioactive isotopes of Nitrogen
Nitrogen has 15 isotopes from 10N7 to 25N7. Among these 15 isotopes three isotopes (13N7, 14N7 and 15N7) occur naturally due to lightning and rest are artificial isotopes. Among the natural isotopes only 13N7 is radioactive isotope with half-life of 9.965 min.
| Isotope of Carbon | Stability | Half-life | Decay | Daughter Isotope |
| 13N7 | Radioactive | 9.965 min | Beta+ | 13C6 |
| 14N7 | Stable | – | – | – |
| 15N7 | Stable | – | – | – |
Radioisotopes of Nitrogen have not much uses, but N-15 is used in NMR spectroscopy.
Radioactive isotopes of Iodine
An Iodine atom has 37 known isotopes from 108I53 to 144I53. Among these 37 isotopes of Iodine only 127I53 is stable and rests are radioactive isotopes. The I-129 isotope is most stable among the unstable radioactive isotopes. This isotope has the half-life of 15700000 years and decays into xenon (129Xe) after emitting beta+ ray.
Most of the radioactive isotopes of Iodine are used in medical science.
Radioactive isotopes of Potassium
Potassium has total 26 known isotopes from 31K19 to 57K19. Three (39K19, 40K19 and 41K19) of these occur naturally. Among these natural isotopes 39K19 and 41K19 are stable isotopes and only 40K19 is long-lived radioactive isotope. 40K19 decays mostly (89%) into 40Ca20 after emitting beta particle.
| Isotope of Carbon | Stability | Half-life | Decay | Daughter Isotope |
| 39K19 | Stable | – | – | – |
| 40K19 | Radioactive | 1.248×109 years | Beta– or Beta+ | 40Ca20 (89%) or 40Ar18 (11%) |
| 41K19 | Stable | – | – | – |
Uses of radioactive isotopes of Potassium
- 40K19 to 40Ar18 decay is used in Argon dating of rocks.
- Minerals are dated by the concentration of potassium and the amount of radiogenic 40Ar18.
Radioactive isotopes of Uranium
Uranium is a naturally occurred well known radioactive element. It has total 27 isotopes from 214U92 to 242U92. All of its isotopes are radioactive in nature. Among these isotopes U-238 has maximum natural abundance with 99.2739%-99.2752%.
| Isotope of Carbon | Stability | Half-life | Decay | Daughter Isotope |
| 234U92 | Radioactive | 2.455×105 years | Alpha | 230Th90 |
| 235U92 | Radioactive | 7.04×108 years | Alpha | 231Th90 |
| 238U92 | Radioactive | 4.468×109 years | Beta– (twice) | 238Pu94 |
Uses of radioactive isotopes of Uranium
- Uranium is widely used in high-density penetrators in military sector.
- Uranium has the applications as the thermal power source in nuclear power plants.
So, in this article, we have discussed the radioactivity of isotopes of radioactive elements and their uses. This is all from this article. If you have any doubt on this topic you can ask me in the comment section.
Thank you!
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