hello everyone welcome back to this Channel today we're going to look into a level physics structure of the atom and fundamental particles and this is the chapter outline now let's start off with some history of nuclear physics so the Greek philosopher democratus proposed that all matter is proposed of this tiny little atoms here and he believed that these atoms are different in terms of size shape and also motion forming the foundation of matter and soon after JJ Thompson discovered that there is an internal structure within each these atoms and he called it the plum pudding model in which within each atom it consists of positively charged proton and negatively charged electrons and he hypothesized that this is how it's going to look like when alpha particle is discovered it is used to prop the atom structure and by observing how this little particles interact with the alpha particles scientists have figured out that Plum puding model is not the correct model which leads to Ernest rord experiment so this is how the experiment look like a beam of alpha particles were directed at teen shets of go foil and there's this circular fla screen that detect the particle's trajectory and when particle hit the screen they created tiny flashes of light indicating the deflection angle okay this is the outcome of the experiment most particle pass indicating that atom mostly consists of empty space and some particles were deflected but only slightly and it occur when the alpha part particles pass through near the nucleus they are deflected because they are repelled and some a tiny small fraction of alpha particles they literally take a you and this happen when alpha particles directly collided with the dense positively charged nucleus so significance of the outcome is that erest disprove The Plum Pudding model because if atom is a plum ping model alpha particle would just pass straight through and there should be no deflection because it's much heavier what the outc come says is that hey atom should look like this which is what we known as the nuclear model Solar System model in which the atom mass and positively charged are concentrated in a small dense nucleus which explain why the particles were deflected so now we know that this is how an atom look like internally the next few minutes I'm going to talk in depth about the particles that is inside an atom so first of all let's understand the atomic skill so it is quite inconvenient to say that well the radius of a proton 10 to power -10 this is why scientist has created a unit called and it stands for 10^15 and it allows scientists to communicate easily and for electrons here they are always considered as having zero size because they are very very small now calculating proton density we know the mass of the proton and we know the radius of it so we can use the radius to calculate the volume which will help us to figure out the density of a single prot as you can see here the number is very huge and a proton is approximately 10 to the^ 14 and 15 times dense than ordinary objects so they are very dense particles so that's all about proton let's move on to nucleons so nucleons are the particles inside the nucleus it includes the protons and the nucleon whereas nucleon number is just the number of protons and nucon in the nucleus so in this case my nucleon number will be seven another thing that you need to know is that the concept of unified atomic mass unit so this unit is one2 of the mass of carbon the reason why we do 112 is because carbon contains six protons and six neutrons and by doing one 12 of carbon 12 atom we approximate the mass of a single proton and neutron the reason why we use UniFi atomic mass is also very similar to why we use one fantomet is to avoid extremely small values when we are stating their number so instead of saying 1.7 * 10^ -27 we could do 1.007 U which helps us to compare two particles easily now you also need to know about what nucle and nucle notation is nucle is a specific type of atom defined by its number of protons and neutron and this is how the notation let just give you some example the numbers here represent the number of protons and the number here represent the number of nucleon which is the sum of protons and neutrons another concept is TOS this is the atom with the same number of protons but different number of neutrons they have the same chemical properties but they have different nuclear properties different number of neutrons also mean that they have different mass density and boiling point so these are some example of isotope hydrogen carbon chlorine uranium and neon well so far the atom that we look at they are neutrally charged so how do we create ions we have a positive ion if there are more protons than electrons it means that one of the electrons might have get knock off and the atom will turn to become a negative ion if there is more electron than protons so that's all the basics you need to know about what's inside an atom now let's look into something more invis which is the nuclear force nuclear force is a powerful force that bind protons and neutrons in the nucleus it's a force that holds them together and what it does is to overcome the electrostatic repulsion because these are positively charged proton they naturally they should repel each other so to make sure that they are together we have nuclear force and the key point is that it acts over a very short range only within the nucleus so a large nucleus tends to be unstable because more protons and electrostatic repulsion will be greater so neutrons are the one that counteract the instability and by providing additional nuclear force without increasing repulsion because they don't have charge so stable nuclear often have equal number of protons and neutrons and for larger element it requires more neutrons than protons to offset the repulsive forces Neutron to proton ratio will increase with atomic number however scientists found out that nucle with more than 83 protons they are inherently unstable no matter how many neutrons you have for example uranium 238 understanding the stability of an atom help us to understand how radiation occur so Henry beerer discovered radiation while studying phospher material he observed that uranium swords emitted energy that could Fork photographic plate even without sunlight and the other scientists they expanded the study discovering polonium and radium all right so in this video we're going to learn about alpha beta and gamma rays they are emitted by unstable nuclei of atom so just now we learn when an atom will become unstable so the reason why we want to learn that is because it relates to radiation so to achieve stability the nucleus will release radiation trans forming it into a more stable state so these are the characteristic of the three types of radiation alpha particles they are the heaviest this is a symbol they are made out of two protons and two neutrons beta particles made out of only one electrons something new for you is beta plus particles which we call a positron it is just an electron but it is positively charged gamma ray is just a electromagnetic radiation so more characteristic here that's their speed you can see alpha particles is the slowest and and GMA is the fastest of their mass as well and this is how they can penetrate through different materials just an illustration to show you that alpha particles has the least penetrating power whereas gamma ray has the most penetrating power all right let's dive deep into what's the characteristic of alpha particles first of all they are heavy so they move at a slower speed and they are made out of two protons and two neutrons and they are released when an unstable nucleus releases an alpha particles so high ionization they can ionize atoms really easily transferring energy and losing momentum short range they can only travel a few centimeters in air that's because they are being absorbed by atoms easily for beta particles they're much smaller and they ionize atom less effectively because they have less Char and they travel through material much easily compared to alpha particles they can penetrate up to a few millimeters of human tissue and absorb by 1 cm of aluminum so in your igcs you should have learned the characteristic of beta Decay and this is how it looks like beta Decay happen when there is too many neutrons in the nucleus and the neutron de Decay into proton and an electron which is released as beta particle and what's new for you is that it could also be that the nucleus has too many protons and this protons turns into a neutron and a positively charged electron which is emitted as beta plus particles we call it positron now what is positron it's called an anti particle of the electron it has the same mass but it carries a positive charge and it consists of particles that are opposite of ordinary matter particles so electrons negatively charged positively charged and positron and electrons means destroy completely upon contact releasing energy as gamma ray which lead us to gamma ray so gamma ray is a form of electromagnetic radiation so it at the end of the electromagnetic spectrum and they have no mass and no electrical charges and they have low ionization but High penetration because they are so quick they penetrate quickly that's why they they couldn't ionize that effectively as Alpha and beta particle also because it has no charge and they are emitted after Alpha and beta Decay and after the emission the nucleus will become a more stable atom well having talked about the different types of radiation we will now talk about the energy involved in this radiation as for alpha particles let's say there are many alpha particles being they will all have the same kinetic energy they move at the same speed whereas for beta particles before you understand how it varies let's understand a term called electron volt so an electron volt is the energy gained by the electron when it is accelerated through a potential difference of one volt so this is the amount and that's basically the amount of a single charge one colum of charge and the way we calculate is V = to W / Q so what is the energy gained by the electron which is the work done when it is accelerated through a potential difference of one volt so if you rearrange the formula you will get the same value and the reason why we want to use electron volt is so that it helps us to represent tiny energy spatter so previously we have learned about fantomet we have also learned about UniFi atomic mass so now electron volt they all serve the same purpose to avoid using extremely small value so just now we mentioned that alpha particles they all have the same kinetic energy for beta is a little bit different it do not have consistent energy this is because during beta Decay the energy is not just is gained by the beta particle some of it also go to the electron anti neutrino and what is an electron anti neutrino it is a nearly massless chargeless particles emitted it carries Away part of the energy which explain why beta particles have varying energy so the particle released during this positive animation is known as electron neutrino which is this electron neutral so for all the Decay they all obey the same law conservation of protons and neutrons so if you look at alpha decay before and after the the number of nucleon and the number of protons are conserved 234 + 4 2 38 90 + 2 92 same goes to Beta minus Decay even though they have released one more electron the original nucleus has one additional proton to balance out the electron beta plus is the same left hand side equal to right hand side and this is the antin neutrino which has no charge however one thing you do need to know is that in this process mass is not conserved meaning if before the reaction is 1 kilog after the reaction it could be 0.99999 kog and where where does the loss Mass go according to the equation eal to mc² the loss Mass has been converted into energy now the last part of the chapter we're going to talk about subatomic particles initially electrons proton and neutron they all considered fundamental particles because they are so small so scientists begin to uncover more particles that didn't fit this simple pattern they realize that is a much more richer subatomic world and how they discover it is through cosmic ray high energy particles from space interacted with Earth atmosphere producing unexpected particles and they are captured by the scientists as meon and peon they also use particle accelerator and this accelerator like the large hron collider reveiew new particles like and they review new particles like quacks gluons and bosons which I'll talk about what are they in a while so families of particles this is something that scientists came out with and there are two types of particles leptons these are the fundamental particles that do not experience strong strong nuclear force like electron and neutral whereas hyro which is something we'll dive deeper into is they are made up of qus helped together by strong nuclear forces like bons include protons and neutron and mesons and kione so scientists discovered that quacks are fundamental particles that combine to form hron like protons and neutrons so they have charges less than the fundamental charge so instead of one colum they have two over three 1 over three they never exist independently always fine within a hron and they combined to form hron with charges equal to e or multiple of e there are six type of quacks which I will show you in the next slide so the six type of quacks are up down charm strange top bottom you can see that each type of quacks they have different amount of charges so this characteristic Define the behavior of hyrons so this is how they can combine together a pro is no longer known as the fundamental they're made up of two up quacks and one down quacks whereas Neutron is made up of one up Quack and two down quacks so we also have another type of hyrons like P and fi so these are their compositions so if we were to look closer to Beta Decay a neutron is converted to proton emitting and electrons so if you want to discover the equation at a quack level this is what it looks like so one down quax of neutron is being now converted into U up quack plus an electrons plus an anti so that's the end of nuclear physics thank you so much for watching I shall see you in the next video goodbye