Radioactivity

Radioactivity is a very interesting phenomenon, which has transformed the power resources to the highest degree! Your misconceptions about radioactivity will be cleared after reading this blog, and your basics concepts will be polished!

Some History: Radioactivity was discovered in 1896 by A.H. Becquerel

Radioactivity is a process by which an unstable atomic nucleus loses energy by radiation. An unstable atomic nucleus here means an atomic nucleus whose internal and external forces are not balanced. This basically happens either due to an excess number of protons or neutrons.

Only certain combinations of neutrons and protons are stable in an atomic nucleus. The stability of an atomic nucleus can be defined as a balance between strong nuclear force and electromagnetic force.

Neutrons hold protons together with help of strong nuclear force, whereas, protons repel each other due to electromagnetic force since they possess same charge. The strong nuclear force is able to overcome this electromagnetic force only at very small distance, like that between neutrons and protons. Also, the electromagnetic force and strong nuclear force are balanced out.

Therefore, the number of neutrons needs to be increased with an increase in Z.

Let’s suppose that number of protons is increased, whereas the number of neutrons isn't sufficient against the number of protons. Such an atomic nucleus is called an unstable nucleus.

Any element which has an unstable nucleus is termed as a radioactive element

Only certain combinations of neutrons and protons are stable in an atomic nucleus.

 Stability of an atomic nucleus can be defined as a balance between strong nuclear force and electromagnetic force.

Neutrons hold protons together with help of strong nuclear force, whereas to protons repel each other due to electromagnetic force since they possess same charge. 

Strong nuclear force is able to overcome this electromagnetic force only at very small distance, like that between neutrons and protons. Also, the electromagnetic force and strong nuclear force are balanced out.

Therefore, number of neutrons needs to be increased with an increase in Z.

Let’s suppose that number of protons is increased, whereas the number of neutrons isn't sufficient against the number of protons. Such an atomic nucleus is called unstable nucleus. There can be two cases in this nucleus:

1. Strong nuclear force is very large as compared to Electromagnetic force, arising due to large number of neutrons, as compared to number of protons.

2. Electromagnetic repulsion dominates strong nuclear force, due to a very large number of protons as compared to number of neutrons.

This leads to the disintegration of nucleus. After large number of neutrons, also because of very small distance, the Strong Nuclear force dominates

We know that atoms of elements try to be stable. In case of non-radioactive atoms, they lose their valence electrons or gain them in their valence shell to obtain a stable configuration, but in case of unstable nuclei, they release energy in form of radiation and become stable.

Radioactive decay, as the name suggests, is a random process in which the nucleus of an atom decays i.e. disintegrates. This basically includes emission of a particle like alpha, beta particles or photons. Although time of decay of particles cannot be predicted for individual atoms, it can be predicted for a group of atoms, which is particularly expressed as decay constant, the overall decay rate for the atoms.

The Law of Radioactive Decay suggests that the number of nuclei which will undergo radioactive decay will be directly proportional to the total number of nuclei in that sample.

You might be thinking what the hell is this decay? Well, decay, often called Exponential Decay, is the process in which an object's current quantity decreases over a period of time. The decrease rate is proportional to the current amount of an object and inversely proportional to the time taken.

         

                      ∆N÷∆T = -JN Eq(1)

Here, N is the quantity of object calculated at the beginning of the reaction, and T is time.

The above equation represents an exponential decay, which undergoes integration to be solved.

                       N(t) = N(o)e^-JT

Here, N(t) denotes the quantity of that object which undergoes decay, N(o) represents the quantity of object at the beginning, e is the Euler’s number ( here 2.718 ), and T is the time. J is the decay constant.

By Eq (1), you may deduce that it is roughly the rate at which an object’s quantity decreases per unit time.

Henceforth, larger decay constants eventually mean that the objects will disappear quickly.

For instance, Higgs Boson has a really large decay constant, and it lasts only for 1.56 X 10²² seconds approximately! 

Poor Higgs Boson, it can't even celebrate its birthday.

Coming back to the topic, you should know about the types of radioactive decay, and all types of them release energy in a large quantity.

Types of radioactive decay that have been observed are :

1. Alpha decay: In this type of decay, the unstable nucleus loses 2 neutrons and protons. Hence, Z decreases by 2, leading to the formation of a new element! Also, the ratio of protons to neutrons decreases, although by the same factor, but allows a more stable ratio of protons to neutrons.

2. Beta – decay: In this type of decay, a neutron converts to a proton, leading to release of Electron and an Antineutrino. This reduces number of neutrons and increases number of protons, by a factor of 1 each, providing a more stable proton to neutron ratio

3. Beta + decay: In this type of decay, proton converts to neutron, and a positron and neutrino is released. This decreases the number of protons

4. Gamma decay : This takes place after the former decays, or sometimes after the latter decays too! Basically, the nucleus is left in a really excited state. A lower state nucleus is achieved by emitting a photon of gamma-ray, having energy usually more than 100 keV.

5. Neutron Emission: This primarily occurs with nuclei beyond the nuclear drip line. In this decay, a neutron slowly and slowly decays away, as a part of neutron emission. This decay occurs in nuclei which is rich in neutrons. Neutrons, therefore, decay in such cases, and it is only possible because neutrons in a nucleus have comparatively more energy as compared to a nucleus and neutron(s)

6. Electron capture: This might not seem the best way of decay, but the mechanism behind this is quite interesting. A free electron is pulled by the nucleus and causes a proton to convert to proton, simultaneously releasing a neutrino and guess what : gamma ray

7. The Lazy Method : Lazy method, as I'd like to call it, is a decay in which a nucleus heavier than an alpha particle is released….quite nice and quick way to get rid of unstable nuclei!

All elements in the 7th period are radioactive in nature!

Radioactive elements are of immense importance since they serve as a really important source of energy. They should be judiciously used since they are non-renewable and rare. 

Pic source @paixails

Article by @ojjas