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Radioactivity

Generally, When we listen to the word radioactivity few things strikes our mind.  The main thing that strikes in our mind is Fukushima, Russia, China or some big countries with nuclear bombs or perhaps a nuclear waste site. This article focuses on what is radioactivity, how it works, forms of radiation, its application and risks.

Definition 

Radioactivity is the emission of subatomic particles or electromagnetic waves from the nucleus as a means of staying stable. Before going to why atom emits radiation, I would like to explain few terms.

Isotopes

Isotopes of a certain element are the one with different nuclear formulae for the same element. And we know that the different elements, for each element have to have the same number of protons. In the case of isotopes, it has the same amount of protons but different amount of neutrons. This means that the same element can have different atomic mass because the proton number and atomic numbers remain same. 


 When we look at the figure above, the figure of Helium 4 which is an isotope of Helium, it has two protons and two neutrons and its atomic mass is 4 and it has got two electrons orbiting around the nucleus.  Now, when we look it Helium 5, also an isotope of Helium, we can see 1 additional neutron inside the nucleus, and it still has two protons which makes it chemically same as Helium. Finally, those are the isotopes, which have a different neutron number of the same element.
 

  • Force Inside the Nucleus
               We learned from electricity that opposite charge attracts and like charges repel. And we also know that protons are positively charged and neutrons have no charge. So, if we take into account all of the protons in the atomic nucleus the question may arise, how does the nucleus stay intact without all the protons spontaneously repelling each other?  There is a strong nuclear force inside the nucleus which binds all the nucleons with other nucleons that are directly next to each other. Basically, strong nuclear force attracts protons with protons, attracts neutrons to neutrons and attracts protons with neutrons. It binds these nucleons together. Next force is the electromagnetic force, or we can call it the cool on a force which attempts to repel like charges from each other. Electromagnetic force has more dominance over the strong nuclear force, but the reason the strong nuclear force is called that is because it is so strong, much stronger than the electromagnetic force. The electromagnetic force is attempting to rip apart the nucleus, whereas the strong nuclear force is attempting to bind the nucleus together.

  • Radiation Emission Process

When we look to the element such as Uranium, which has incredibly large nuclei. In Uranium every single nucleon is attracted to every other nucleon right next to it by the strong nuclear force. But at the mean time, it also repel to every other proton in the entire nucleus by the electromagnetic force. As the nucleus get bigger, the more dominant is the electromagnetic force. That is why some nuclei are unstable, they tend to break apart and they emit radiation . By emitting the radiation, the nucleus is able to decrease its mass and turn itself into a lighter element, which means the nucleus is no longer at risk and  electromagnetic force is no longer overpowering the strong nuclear force. Finally, giving out the radiation is simply an attempt by the nucleus to save itself from immediate destruction by the electromagnetic force.

 

  • Different Forms of Radiation

When we look at the atom, sorry inside the atomic nucleus, both proton and neutron have the relative mass of around one. The proton has the positive charge of magnitude 1 and Neutron has 0 charge which means Neutron is completely neutral. Electron, which is not found in the nucleus, but it is orbiting around the nucleus has a very negligible mass of 1/1836 (compared to proton and neutron) but its charge is significant and has the negative charge of magnitude 1. We have learnt in chemistry that atoms have no net charge because there is an equal amount of protons and electrons, therefore giving zero overall charges since they cancel out.

    • Alpha Radiation

As explained earlier, when atoms get too big they want to shoot out some of their nucleons to save themselves from exploding. This is the one way, they shoot out from a helium nucleus, basically they shoot out two protons and two neutrons therefore making the atom lighter and transforming it into a different element.

When a nucleus emits an alpha-particle,since  it loses two protons it turns into different particle which of course has the two proton less. And since it loses four over all nucleons, its mass decrease by four. Above figure explains that a Uranium(238) nucleus has 92 protons and 238 nucleons in total.  It sheds two protons with the alpha particle. Therefore, the resulting element has ninety protons and it loses four nucleons in total so the resulting isotope has 234 nucleons in total. In this case, when Uranium 238 emits an alpha particle, it turns into Thorium (234) with atomic number ninety and mass number 234.

    • Beta-Radiation

Beta Radiation is simply the emitting of an electron. As we know the electron has the negative charge of magnitude 1, therefore the overall charge of the particle is -1. As said before, the mass of an electron is 1/1836, so the overall mass of the particle is also 1/1836. When the electron is emitted, something special happens on the nucleus i.e a neutron turns into a proton which is quite strange. This means the mass number won’t be change rather it will stay completely the same. But the element is going to change because 1 more proton is going to introduce.


The above figure show that when the Thorium(234) emits a beta particles, the result is Protactinium in which it has the same mass number as isotopes but has one more proton. Symbol of beta particles show that it has zero mass but has atomic number of -1.

    • Gamma-Radiation

Gamma Radiation is the third form of radiation. It is special types of radiation because it does not emits any particles. It shoots out electromagnetic waves which is in, in itself. Since it’s a electromagnetic wave it does not have charge and it does not have any mass. Nucleus remain completely same after the gamma radiation.

    • Background Radiation

Background radiation is kind or radiation we feel all the time. It’s a kind of radiation that comes from common sources. We call it background radiation because it does not present any effect that are visible to us but it is practically everywhere. We will not be able to feel it and we won’t even know it is there. Some sources of the background radiation are radon gas, x-rays and tracking equipment used in hospitals, Nuclear explosion, cosmic rays.

  • Application of Radioactivity

There are many application of radioactivity which are makes our life easier. They are used in field of education, health, production of energy and for monitoring purpose in the industries. Some of the application are described below.

    • Tracers

           Radioactive tracers are those which contains radioactive atoms which facilitates the easier detection and measurement. Traces are basically used in the field of study of plants and animals and also in the medical field. For example, Radioactive Iodine 131 helps us to study the function of thyroid gland.

    • Nuclear Reactor

Nuclear reactor is one of the best example of radioactivity. It controls the fission reactions and helps in producing of energy. Nuclear power house uses uranium in fission reaction to produce energy.

  • Risk of Radioactivity

Beside the good application there is also risk of radioactivity. The major risk is in our health. Radioactive particle can easily get inside our body, it can damage some of the biological cells. This can cause fatal cancer to develop, or if it get into reproductive cells, it can cause genetic defects in offspring.



 

References

 

http://outreach.atnf.csiro.au/education/senior/cosmicengine/images/sun/betadecay.gif

 

http://www.phyast.pitt.edu/~blc/book/chapter5.html

 

https://www.nde-ed.org/EducationResources/HighSchool/Radiography/usesradioactivity.htm

 

http://www.atnf.csiro.au/outreach//education/senior/cosmicengine/images/sun/alphadecay.gif

 

http://www.universetoday.com/45096/alpha-radiation/

 

http://www.blackcatsystems.com/GM/experiments/ex7.html

 

http://www.epa.gov/radiation/understand/beta.html

 

https://www.nde-ed.org/EducationResources/CommunityCollege/Radiography/Physics/gamma.htm

 

http://www.stmary.ws/HighSchool/Physics/home/notes/modPhysics/ForcesInsideNucleus.htm





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