hello jc1 this is the second topic of the H2 syllabus today we'll be doing atomic structures um just like the previous lecture notes on the first page of the lecture there will be a series of assessment objectives whereby you can look through at the end of the lecture and see if you're able to answer um the following um objectives so now let's take a look at the overview of the lectures so for the first lectures I will cover content point one and two and then lecture two I will cover point three and four and lastly for lecture three we'll talk about point five before we begin um I would like you to take a look at the evolutions of the atomic model so you may want to actually take a look at the video on page three to understand more about how scientists actually developed um and come up with theories of um the atomic model all right so for the interest uh in the interest of time I'll not show you the video here but I think it's actually quite interesting if you can look through um across the years how the scientist actually finally come up with the final model of the quantum model which is by the a wind now let's take a look at sessions 1.2 section 1.2 talk about the fundamental subatomic particles of matter this is not something new to you so we always know that an atom is the smallest particle of an element that retains its chemical properties and what does the atom contained um in the nucleus is make up of protons and neutrons collectively know as nucleons all these are actually recapped based on your Secondary School syllabus the nucleus is then surrounded by negatively charge electrons and these electrons occupy regions in space which is known as orbitals which going to talk about it later on and of course the electrons are attracted by protons by electrostatic forces I would like you to take a look at the table below so you can take a look at um the particles the sub atomic particles the charged the relative charged Rel the rest Mass relative mass and of course the location in the atom um I think maybe there's what two question that you be pondering what's the difference between the rest mass and the relative mass so first of all if you can take a look at the relative mass there is no units as for the rest Mass it is in terms of kg so what exactly is relative relative mass is talking about the ratio of the mass of let's say proton is to Neutron is to electron so it will be 1 is to one is to electron will be 1 over 1840 so relative mass um if I were to reiterate create the difference between relative mass and rest Mass would be relative mass there's no unit and rest Mass that's a unit relative mass basically is just a ratio of um the masses so next question you wondering will be can this information be found in the data booklet I would like to turn your attention to your data booklet you can take a look at page one page one here this um session one talk about the important values Conant and standards I have highlighted yellow green and and blue so these are where we can get the rest mass of the respective sub atomic particles here so you can see like the rest mass of proton will be 1.67 * 10^ minus 27 kg so in other words that's only need for you to remember the exact rest mass of proton neutrons and electrons but you can take a look actually electrons are relatively smaller I mean lighter than protons and neutrons now let's take a look at section 1.3 section 1.3 talk about the behavior of the beings of protons neutrons and electrons in an electric field we are supposed to deduce the behavior of how these subatomic particles behave in the electric field now let's take a look at the diagram here okay as the word suggested electric field when we draw we annotate by this line here which I noted by the rig light and electric field there are different polarity so we actually annotate by the positive plate and the negative plate here and if you take a look here first you pass through the beans of the subatomic particles like electrons protons and neutrons and I would like to draw attention to is that deflection will only occurs when the charge particles enter the electric field so where is the electric field it is the one of annotated highlighted in green so that's why you will see deflection actually started at a point whereby Enter The Green region okay so I believe this is quite common sense electrons which are negatively charg will then be attracted to the positive potential of the electric field right uh we learned in Primary School the oppositely charged particles will attract each other likewise proton which is positively charged will be attracted or deflected towards the negatively potential okay so this is proton so proton will be deflected towards the negative plate and electron which is negatively charged will be deflected towards the positive plate so you can see both the proton electron will move in a straight path after they leave the electric field so where is the ending of electric field is actually I'm going to anate with this is actually here so this is at the end of electric field all right so Neutron will not be deflected at all because it is neutral so this is pretty Common Sense next I want to talk about the angle of deflection angle of deflections is dependent on the relative masses and charges of the particles and if you want to compare the angle of deflections it is directly proportional to charge over Mass so if you take a look at this so-called um expression per se the particle with lighter mass or higher charge will have a greater angle of Def so example you will realize that the angle of deflection for electrons will be higher than the one with proton because electrons have lighter Mass that's why it will deflect at the greater angle I would like you to take this down this is useful for calculations so this one stand for the angle of deflection in the electric field of course so this talking about about let's say a sub particle one over sub particle 2 so charge over Mass so these socaled formula and um allow us to determine the angle of deflection for any particles so let's say if um you given two particles one is unknown one let say is proton for example all right so for this page what I talk about 1.2 what's important about SE sorry about session 1.3 is you know how to draw this as in how the beings of protons neutrons electrons they will behave in electric field next we talk about uh the angle of deflection which is D directly proportional to charge over Mass lastly at this juncture um as you still very new to your lecture note you will see something like cell check uh in your lecture notes so what's the purpose of cell check okay cell check allow you to do cell d learning whereby you need to attempt the questions and check the answer all the answer have been uploaded on our Google Drive whereby you can attempt the question and check the question these question will not be discussed in tutorial in tutorial we will only discuss um discussion questions so cell chart question is this question one all right so please attemp this and check your answer on the Google Drive okay next I'm going to talk about uh section 1.4 what um what are the important points for 1.4 okay so for 1.4 you're supposed to deduce the number of protons neutrons and electrons present in both the atoms or the ions given a proton or the nucleon number and of course you're supposed to describe the contributions of protons and neutrons in the nucleus in terms of the number and the nuclear number okay now let's take a look at the first representations of how we represent a particular symbol of element so they say the atom of an element can be represented as a following so the symbol symbol of the element then is a nuclear number which is also known as as a mass number atomic number is also known as the proton number so proton number is unit for each element um so if you know the proton number this will give you the identity of the element all right so it also give us a number of proton in the nucleus of an atom I like to draw your attention to how uh we symbolized uh element in periodic table it's slightly different if you take a look at periodic table basically you just follow the legend here okay so the first number here is actually the atomic number which is a proton number then uh we have the relative atomic mass all right so relative atomic mass is actually yeah so just take note of how uh the are being uh represented in the periodic table okay uh now let's continue to take a look at some of the definitions so nucal number which I just mentioned is also referring to the mass number so what is mass mass number is total number of protons and neutrons in the nucleus of an atom so in other words number of nucleons or rather we say nuclear number equal to the number of protons and neutrons okay so this is not something new as well we have learned this in secondary school okay so if you take a look at the next box uh in the neutral atoms the number of protons will be equal to the number of electrons however when atom gains electrons a negatively charged ions or another n ion is produced so when n ion is produced how would the number of electron change so I want you to take this down if it's talking about n ions the number of electrons will then be equal to the number of proton plus one right because it means that you have more uh electrons than protons if you have a c the number of electrons would then be less than number of protons right because k actually loses electrons so it be equal to number of protons minus one that would be equal to number of electrons likewise at this juncture you can do cell check question two to cell check question four to check your understanding for the following uh session that I've discussed okay now I'm going to take a break before I move on to part two um um before we take a take a break at the part two of uh lecture one I would like to continue on the one last part which is on 1.5 which is on isotope again um this is not something new we have learned isotope in secondary school you have to know how to distinguish isotope based on the different numbers of neutrons present first up let's take a look what exactly are isotopes so Isotopes are atoms of the same element with the same number of protons but the only difference is they have different number of neutrons of course it will result in number different number of nucleon as well so these are just example of Isotopes these are the common example isotop for example you have carbon 12 carbon 13 uh if you can take a look at isotope they have the same number of proton number if you take a look at carbon isotope they all have the same number of proton number all right so the only difference between the isotop is that they have different number of neutrons okay so these are just an example of how uh you can work out the number of a neutrons next we take a look at the relative atomic mass of the element why is it often not a whole number this arises due to the presence of Isotopes occurring in different percentage abundance if you forgotten what this this refer to topic once of the More Concept and stet right in summary that's what I talk about here so the number of protons I mean is equal translate that to identity of element and number of proton will be equal to the nucleon minus of the number of neons and we also learned that what Isotopes Isotopes are elements same elements same number of protons but different number of neutrons as well as different number of nucleon numbers so with that we will take a break from um the first part of the notes and please come back for the second part of lecture one