Hey, hello. Welcome to Chemistry. Actually, to be very frank, complete spectroscopy has got two uses. The first use is that you can find out actually the quantity of any substance present. Second is you can find out the structure of any molecule by spectroscopy. I give you an unknown compound, so you can find out the structure of that unknown compound. One of the spectroscopy that we have seen in previous lectures is called IR spectroscopy. Ir spectroscopy, you can tell you about the present functional group in the molecule by using their spectroscopic can tell you because you read about their vibrations. Every functional group has got a particular vibrational frequency that it absorbs. Now, coming up to NMR. Nmr's most use is to predict that if a distinct atom is present, then it will be present in so many different forms and in different environments. What I'm saying is, you may not understand it, but in the coming time, when you start to study NMR, you will start to understand these things about NMR. Now, if you look at the NMR word, that nuclear magnetic resonance spectroscopy, it will give you three words. The first word is called nuclear, which means it will deal with a nucleus.
The second word which comes in is magnetic, which means it
will have a significant influence on the magnetic field, it has a big
influence. And the third word is resonance. Now, this resonance is not the
resonance of organic chemistry, where you will study canonical structures. This
resonance is somewhere in physics, where you see that when two things have a
frequency or energy match, then we say, brother, the resonance is done. This is
that resonance. Now, if you want to study NMR, whatever you take out, NMR is
directly started and that directly comes on spin or directly tells you the
generated energy states. The NMR that we will study here, we will start from a
very basic level. Maybe my starting, those videos, I'm not interested in
graphical graph solving or molecular elucidation. I am more interested in
understanding NMR, the basic principle behind NMR. Nmr, what basically do you
understand by NMR? So let's start first. Atom is very important because, in my
NMR, there is the word nuclear. And nuclear means I am somewhere related to the nucleus. So if you want to understand the nucleus, let us get into the structure of
an atom. Let's try to understand the atom.
If I try to draw the structure of an atom, so if this is my atom, which I make in a plane, and I know there is a nucleus somewhere in between. I have got something called the nucleus. This nucleus is made up of two staff. Actually, this nucleus is made up of many things. I will be wrong if I say it is made up of only two stuff. There is something called subatomic particles. Now, subatomic particles, we have never heard of them, electron, proton, neutron. There are many subatomic particles. And today's modern physics has to complete the nucleus. It has to be the core of the universe. It wants to crush the nucleus and get rid of its subatomic particles. But basically, I can say that I have two subatomic particles in my nucleus, one is a proton and the other is a neutron. And I know my proton is positively charged and my neutron is neutral. Because of this proton, I have got something called electrons. I will tell you in the coming videos. Now, these are electrons. These are electrons. These electrons are under a negative charge. Because of this, say they are called charge particles.
Protons are charged particles and Electrons are charged particles. Now, basic physics tells me that when I started with the electron, then I understood that the electron started, then this thing was understood that the electron not only spins around the nucleus, but it spins in its own place. The way the Earth, the Sun, is circling it and it is not only circling, it is circling in its own place. Similarly, my electron is also rotating in its own place, which is called spin. These electrons that are standing near me, not only are they will circle around the nucleus, but they will also circle in their own place. If one can move like this, then one possibility is that it can move anti-clockwise, the other possibility is that it can move clockwise. I'm going to draw both these electrons here I have got two electrons, these are two electrons, either my electron can either move in this direction which I will call anti-clockwise, or my electron can move in this direction which I will call a clockwise direction. Now, the problem is an electron has got a negative charge. Now, since my electron spin, every rotating body has got something called as angular momentum
Momentum. Similarly, if my electron is rotating there, then
its angular momentum will be there. The angular momentum is given by the under the root
of small s into small s plus 1h upon 2 Pi. This is completely derived from
quantum chemistry, so I'm not going to a detailed explanation of this formula.
Remember, angular momentum is a vector quantity. It's not only dependent on
magnitude, it depends on direction as well. If I say that my electron is
spinning, it can either spin in this direction or in this direction. But apart
from this, it can also be in which direction spinning. It's in which direction.
It's in which direction oriented. That's very important. So magnitude is very
easy to find out. Magnitude depends on this. Where you notice S is called spin
quantum number. The problem is that in the case of an electron, the value is fixed. In
the case of the electron, S's value is half. The spin quantum number comes out to
be half. Now, there is something again called your spin quantum number.
There's something called a magnetic quantum number. Magnetic quantum number.
This magnetic quantum number will tell you that if the electron is spinning,
the angular momentum of that electron is shown in this formula.
But that electron is oriented in which direction? That is,
in which direction is it spinning? If you have to find out the angular momentum
of that electron in this formula. But in which direction is that electron
oriented? That is in which direction is it spinning? If you want to know that,
then you have to understand the magnetic quantum number. Now, I have a very good
video of it. You will find the complete description in that video as to what is
actually a magnetic quantum number. So click on this link and you will get the
complete description of the magnetic quantum number actually happens. So click
on this link and you will find the complete description of the magnetic quantum
number you can watch it if you want. Now, in the case of the electron, the
magnetic quantum number MS, that's for ME or MSS, that's why I'm writing it
because I'm relating it with spin, will be equal to... It will have two values,
either it will be plus half or either it will be minus half. These are the two
values that are there. We have the basic information about the electron. Now,
after this, in 1924, Pauli was a great scientist, he made this prediction that
the way the electron spins in its own place, that way, my nucleus will also
spin in its own place.
