Most of you who have a bit of science background knows that the atom is made of nucleus and electrons orbiting around it. The nucleus is positively charged and the electrons are negatively charged. In total, the atom is electrically neutral. As I am going to write about nuclear physics, I will talk about mostly about the nucleus and the phenomenons are happening in it. Believe it or not, although the nucleus is so small it has almost all the masses of the atom and it can unleash such an amount of energy that we can light a whole country.

So, what is inside the nucleus? Well, all of you probably know that it is made of protons and neutrons. The proton number defines which elements it is in the periodic table and the sum of the proton and neutron number gives the atomic mass of the atom. But it can happen that two or three have the same atomic number but a different mass number. They are called the isotopes. They fall in the same element in the periodic table just a bit heavier. Sometimes the mass number is the same but they have a different number of protons and neutrons. They are called the isobars Another thing is when the neutron number are the same they are called isotones.

A nucleus can be stable and unstable as well. As you may be already thinking if the nucleus is made of protons and they are positively charged why they are not falling apart as positive charge repel each other. Well, the answer is the nucleus is bind by a force which works on short distance. It is called the strong nuclear force. It is all the time fighting against the electromagnetic force. But in short distance, it is stronger than the electromagnetic force. So, the nucleus exists or we may say we exist. But not all nucleus of every element is stable. The bigger the atom the lower strength the strong nuclear force can have on the protons and neutrons which are far from the center of the nucleus. So, there happens decay or radioactivity. The unstable nucleus will decay until it becomes a stable nucleus. Some can exist in nature and some nucleus can be induced to be radioactive. Induced radioactivity is we make a nucleus unstable by shooting a high energy particle like a neutron to make it unstable and then it becomes radioactive.

Radioactive series

Most of the naturally radioactive elements don't exist anymore as their half-life is less than the age of the earth. But some of them are still there. We divide them into four. There can be a mathematical calculation behind it. Like we can divide the mass number(A) by 4 we get the Thorium series. if you divide by 4 and then add 1 you get the Neptunium series, this way Uranium and Actinium series. Radioactivity is one of the most interesting topics in nuclear physics. It will be interesting to you perhaps when I will start writing about the fission and fusion reactions. As I wrote about alfa and beta decays. I will write here in short but I will write individual posts for them as well. So, alfa decay is actually a quantum mechanic tunnel effect. It tunnels through the nucleus. In Alfa decays the nucleus loses 2 protons and 2 neutrons and completely change into another atom. In beta decay, the mass number doesn't change. It can happen in three ways- Beta plus decay, beta minus decay and electron capture. In beta plus one proton from the nucleus convert to a neutron and it can on happen in the nucleus as it needs threshold energy and beta minus covert one neutron to one proton and in electron capture the nucleus capture an electron from the nearest shell.

Table of nuclide

The important thing is nuclear stability. So, when in the nucleus the proton and the neutron numbers are the same it is more stable. But as the proton number increases the neutron number has to increase more than the proton to compensate it so that the nucleus doesn't break apart. So, if we make a graphical representation between the neutron( in y-axis) and proton (in x-axis) we will find a linear shaped graph until the proton and neutrons are the same. Then it takes a shape of a curve. Bellow the line happens beta plus and electron decay as it wants to decrease the amount of neutron and come to stability. Above the line, its beta minus, just to increase the neutron numbers to be more stable. Then near the curve happens alpha decay and in the end, those heave nucleus decays to come to stability. I will talk next time about nuclear fission and how can we get electric energy from nuclear fusion.

So, that will be all for today. Hope everyone will have a nice week.

References

1. Povh, Nuclei and particles

2. Jean-Louis Basdevant, James Rich, Michel Spiro, Fundamentals in Nuclear Physics: From Nuclear Structure to Cosmology

3. Burcham, Nuclear physics, an introduction