What is Atomic Structure
I will start to dive deeper and we'll start by studying the atomic structure, which is more of a chemistry knowledge. But for the completeness of this topic, we need to rediscover what about atomic structure and why do we know this to understand material science and engineering better. The properties of a material depends on the atomic structure on one hand and the interaction between atoms and molecules on the other hand. Therefore the basic building block of the material will help define the properties, to which the material is being used and also the atoms which are the constituent atoms of the material will interact with each other via different forces. Therefore that will also affect the property. We'll focus on atomic structure to start with and then with the different forces and interactions between atoms and molecules. This necessary the understanding of atomic structure to begin with.
Let us see the very basic structure of a simple atom. We can see here are some particles with a negative charge. Here are some particle with a positive charge and the green particles are supposedly charged last. Let us see each of them individually one by one. The negatively charged particles which seemed to move in orbits around the center is known as Electron. So electrons are basically negatively charged particles.
Types of Bravais Lattice
Properties of Electron in Atomic Structure
What are the properties of electron? Electron is having a charge of - 1.602 into 10 power -19 Coulomb. There is the charge what is the mass of a Ronny's 9.1 1 into 10 to power - 31 kg it's in the art of - 32 kg. Finally as I said, this electron seems to revolve around.
What is Nucleus in Atomic Structure
What is known as nucleus in atomic structure? this is the nucleus of the atom and the radius of revolution. That is the distance from here, the center to this place is in the order of angstrom and that is what defines the atomic size. The distance from the centre to the outermost electron roughly gives you an idea about the atomic size. Let's see what are these positive particles, this positive particles are known as protons and similar to the charge of the electron. Which was negative 1.602 into 10 power -19 protons have same magnitude. But are oppositely charged that is their positively charged and have same magnitude. That point of difference is the mass. The mass of electron was in the order of 10 to power -31 whereas the mass of proton is in the order of 10 to power -27.
There is four orders of magnitude different. So a proton is much more heavier than an electron then third part is as ice'. Mentioned the central region which comes the proton is known as the nucleus of the atom. The nucleus of the atom is in the order of 10 to the power -15 meter so the radius of the nucleus is kind of 10 power -15 meter. Which is a distinctive point of difference from the radius at which 10 electrons revolve around the nucleus. Which was angstrom that is 10 power -10 meter. Let us see the third kind of particle that constitute an atom the green particles. The green particles are known as neutron.
What is neutron in atomic structure
What is a neutron? Neutron is a charged particle there it has zero charge the mass is very similar to that of a proton it's a very very slightly more than that of a proton it is 1.675 into 10 power -27 kg and thereby even a neutron is kind of four orders of magnitude heavier than an electron and the same radius that is the radius of nucleus in the order of 10 to power -15 meter as that of the proton now the interesting take home from here is if you observe the heavy particles that is the proton and the neutron both reside in the nucleus isn't it the very light particles electron revolves in these orbits therefore the mass of the atom almost completely resides at the center or resides at the nucleus of the atom now the proton and the neutron together.
What is nucleus in atomic structure
what is called as the nucleus? So this is my nucleus and in a particular atom if the atom is supposed to be electrically neutral and how is that possible. that is possible only when the number of electrons and the number of protons are same. Thereby the negative charge imparted by all the electrons will be counteracted by the positive charge imparted by all the protons. So in order to maintain the neutrality of an atom, the number of electrons is equal to the number of protons. This whole description is the basic Bohr's model description. In which the electron revolves around the nucleus in fixed orbits.
Let us familiarize ourselves with a few terminologies atomic number. The atomic number represented by a capital Z represents the number of protons. Atomic mass is the sum of the number of proton and the number of Neutron. The bulk of the mass lies in the nucleus that is within the proton Neutron. Therefore the electrons are not going to come into the picture.
A mole is defined as 6.023 into 10 to the power 23 atoms or molecules that is the definition of a mole. An isotope is rather two materials which has same atomic number but different mass number are known as isotope. To give you an example an isotope would be chlorine-35 and chlorine-37. Both have atomic number 17, but chlorine 35 has a mass number 35. Whereas fluorine 37 has a mass number 37. That's why they both are isotopes. So this gives you a brief definition of the different terminologies pertinent with atomic structure.
Bohr's model in Atomic Structure
Next we'll Discuss the Bohr's model. In description we will see what is the limitation of Bohr's model. How that gives rise to what is known as wave mechanical model. What does that mean? While discussing the atomic structure this was the simplistic known as the Bohr's model. In the Bohr's model, the electrons revolve around the nucleus in fixed orbits. So these are the orbits in which the electron revolve around the nucleus. They cannot revolve in any arbitrary orbit. You cannot have an orbit intermediate between two defined orbits. Electron will not be able to revolve in those. So only fixed distances, the electrons can revolve around the nucleus energy of electron is quantized.
Now since we have said that the electrons are revolving around in fixed orbits, the energy level will be defined by the orbit. Therefore the energy is quantized. It cannot take up any value at once. It has to be either the energy level at this radius or the energy level at this radius. The energy level at the next quantum radius. Now this quantization of the locations at which electrons can be present results in what is known as energy states? See over here what you can observe there is an orbit, which is closest to the nucleus in which the electrons can revolve. Then there is a second closest orbit. So there are states of orbit and each state has a particular energy associated with it.
Therefore what we can say is that these are energy states in which the electron can revolve the radius closest to the nucleus. In which electrons revolve is known as the ground state. This is the energy representation for a hydrogen atom drive for home. The point we are using hydrogen atom which is the simplest atom. Because it has one electron, now the electron ideally will be at the lowest energy state. The orbit which is closest to the nucleus and we define the energy at infinity. That is very very far away from the nucleus as 0 electron volt. Then after calculations it is found that for the hydrogen atom at the lowest energy state. The energy level for the ground state turns out to be minus thirteen point six electron volt. But suppose, we give some energy into the electron which is at the ground state.
What it will do, it will absorb that energy and jump to a higher state such that it has sufficient energy to jump from the first state to the second state. Then the energy will increase from minus thirteen point six electron volt to -3.4 electron volt. Similarly, we can increase the amount of energy input and we can keep pushing the electron further away from the nucleus. Each of this state is a energy State, this lowest energy state is the ground state then the first excited state. Second excited state and if you give sufficiently high amount of energy.
What is ionization in Atomic Structure
What is known as ionization can take place. What happens in annihilation the electron is complete rejected from the atom. Electron gains sufficient amount of energy to be freed from the atom. The atom will develop a single and positive charge, because it has lost a single negative charge. So this was the basic idea behind the Bohr's model. Now what is the drawback of poor's Bohr's model defines definitive orbits in which electrons can revolve. But what we know is that any charged particle which is accelerating will lose energy. This is the fundamental one-one of physics. Therefore this electrons which are revolving revolution is accelerated motion. Therefore the electrons should not be able to be moving in the same path. It should slowly lose energy and spiral down into the nucleons that does not happen. Thereby there is some drawback obviously in the Bohr's model which it does not account for this led us to the development.
Difference between Wave and Bohr's Model
What is known as a wave mechanical model and Boh's model? Let's see what does it talk about, The major difference between wave mechanical model and Bohr's model is that Bohr's model defines specific paths. You have a path here or here whereas wave mechanical model says that electrons do not move in specific paths. Rather you have probability distribution of regions where electron can be found. There will be some region where the probability of finding electron is more. There will be some region the chances of finding electron will be less. But you cannot specify that this is the orbit. There will be a range of orbits with probability at different location. This leads to what is known as an electron cloud because you are not specifying where exactly the electron is. It can be anywhere in this whole bound region. This is my nucleus and this way mechanical model comes from the idea that Truong like a wave has a dual nature. That is electron can sometimes you have as a wave and sometimes as a particle.
Let me try, how the probability distribution will look like this is the electron cloud. Suppose that this is my probability and this is my radius. This is the nucleus which is lying over here and I am trying to draw the probability along this path. So what is observed is very close to the nucleus, the probability of finding the electron is almost 0. The probability keeps rising and near the poor's orbit radius. The probability is maximum and after that it starts to decrease again. and it tends to 0 at infinity. So there is a probability to find electrons even at a very far distance.
But the probability is very less the probability to find electron is maximum at Bohr's radius. But it's not hundred percent at poor's radius. There's a clear distribution and this kind of solves the problem which we encountered in the Bohr's model. Whereby accelerated electrons should lose energy and spiral down into the nucleus. So this brings us to the end of the topic on the basic structure of atom. We discussed Bohr's model, the components of a nucleus, the wave mechanical model and how it is better than the Bohr's model.