welcome to chapter 4 part B atoms and elements learning objectives in this part we will discuss the periodic table in details we will discuss ions and atomic mass let's start with the first paragraph we are going to say groups and periods in the periodic table we are going to see the main elements and the transition elements basically the root location we are going to give name to a couple of important groups and then we are going to see metals non-metals and metalloids the periodic table this is the periodic table we saw it again in Part A but here we are going to discuss it in details the periodic table is divided into parts we have this part here and then this part here the elements that we have at the bottom of the periodic table are the inner transition elements there are a lot of exceptions so we will not be discussing in their transition elements at all the periodic table for us it's going to be only this part so when I will be saying the periodic table I will be referring to this part only let's focus when on this part the periodic table the upper part of the periodic table is divided into the main elements and they are these two columns and these six columns from here and the transition elements the main elements follow all the trends we'll discuss the transition elements have a lot of exceptions in the periodic table we have all the elements it's divided in boxes and in each box we have the element symbol the atomic number as we have said the number of protons and then the atomic mass discuss the atomic mass in details later in this chapter the atomic number or the atomic mass of the of the elements is increasing as we are going from left to right hydrogen 1 proton helium 2 protons little trip rod be real 4 protons born 5 6 7 8 9 10 11 protons and etc the Mabel that I told you earlier at the beginning of this chapter that you are responsible for all all elements up to 36 so you are responsible for all these elements for the symbols and names as well as silver iodine barrio and cadmium the atomic number and mass number is increasing as we are going from the upper part of the periodic table to the lower part of the periodic table for protons 12 protons 20 problems 38 protons and etcetera the rows of the periodic table are called periods of the periodic table again the rows of the periodic table are called periods of the color periodic table elements in the same period of the periodic table have similar physical properties so the physical properties of the boron the carbon the nitrogen the oxygen the fluorine the union and etc are similar groups of the periodic table the columns of the periodic table are called groups of the periodic table elements in the same group group of the periodic table have similar chemical properties so beryllium magnesium calcium straw do similar chemistry fluorine chlorine bromine iodine similar chemistry so here similar physical properties here similar chemical properties above its column of the periodic table will have a number we have the 1 the 2 the 3 this is an old system the modern system is using the numbers that we have above here the 1 a 2 a 3 a 4 a and etc these are the numbers of each group so this is the group 1a this is the group 2 a 3 a 4 8 and etc the main elements the main groups have a number and then the letter a and then we have the transition elements with numbers 3 B 4 B 6 B 1 B 2 B etc let's see a couple of important groups that we have for a periodic table these are the halogens noble gases column 8 a helium neon argon Krypton and etc those are inert elements that means that they do not react metals they sign the official solid at room temperature and they conduct electricity and heat they are those that you see in the blue boxes light blue and dark blue as you can tell we have the main elements lithium sodium balloon magnesium calcium aluminum gallium and etcetera and then we have the transition metals skaar don't eat an infant atom and etc cadmium silver and etc nonmetals the nonmetals they do not contact electricity they are usually gases at room temperature and the arrows that you see at the right side of the periodic table in the yellow boxes carbon nitrogen phosphorus as well as hydrogen that's the only exception that we have at the left side of the periodic table hydrogen is a nonmetal in addition to that we have the metal oh it's there they are on the line that divides the metals and the nonmetals they can behave either as metals or nonmetals depending on the conditions those are boron silicon germanium arsenic and etcetera with your exams students will get this particular periodic table the color turn so noble gases we said it earlier they are stable if you want they have stable electron configuration I'm sure that you don't understand them the word electron configuration right now what I want from you is to remember that noble gases column 8a do not react metals tend to lose electrons in order to form cations metals we meet them with positive charge since they in chemical reactions they tend to lose electrons nonmetals here we are data in chemical reactions they tend to gain electrons and to form anions or if you want negatively charged ions but since we spoke about ions let's see them in details we are going to see the charge and how it is related to the number of electrons we are going to say on ization equations and then we are going to predict charges directly from the periodic table ions ions are forms when electrons are moved or added to a neutral atom in other words if you want to form an ion you add or remove electrons you do not change the number of protons in order to form an ion given the fact that electrons have almost zero mass the ions and the neutral species have the same mass how do we calculate the charge the charge of the ion is going to be equal to the number of protons minus the number of electrons let's see an example we have a chlorine atom a chlorine atom we know from the periodic table that it has 17 protons so given that it's neutral 17 electrons nature CH 0 now if that chlorine atom picks up an electron through a reaction then we are going to have still 17 protons and 18 electrons charge minus 1 and that's the symbol that we have we have a chlorine with a negative ion with a negative charge consider a sodium atom it has 11 protons and 11 electrons we know that from the periodic table so net charge zero if that atom loses one electron in a chemical reaction then we have still 11 protons so still have sodium but we will have only 10 electrons in a church plus 1 here we go sodium with the plus charge still sodium since we have still 11 protons but the number of electrons is one less so we have a positive charge and that positive charges one let's see couple more examples fluorine atom nine protons mass number 19 that means 10 neutrons and then it's neutral that means nine electrons the same isotope with a negative charge the number of protons is going to be the same nine the number of neutrons the difference between nine and nineteen then we have the same isotope right the only difference is the negative charge that we have here the negative charge indicates that we have one more Pro electronic sorry one more electron with respect to the number of protons so we have nine plus one 10 electrons the mass number is the same doesn't change 19 let's see another one example barrio 56 protons mass number 137 here it is number of neutrons the difference number of electrons since we are talking about the atom the neutral atom it's going to be the same as the number of protons of 56 this one here has a 2 plus positive charge we have the same isotope the same elements of the number of protons is still 56 still a 81 number of electrons see we have a positive charge that means that we have more protons than electrons so the number of electrons is going to be 56 minus 254 we have more protons than electrons by 2 more protons than electrons by 2 more electrons than protons by 1 the mass number is going to be the same 137 in order to go from the atom to the ion we are removing electrons we do not change the number of protons we do not change the number of neutrons so as we are going from the neutral spaces to the ion the number of protons is the same the number of neutrons is the same so the mass number is the same the only thing that changes is the number of electrons either we add electrons when we have negative charge or we subtract electrons when we have positive charge complete the following game ization equations you may want to pause the video here and try to do this exercises by yourself and come back to correct your answers sodium goes to sodium plus 1 that means that it has here we have more protons than electrons by 1 that means that it has lost one electron here it is also the overall charge before the arrow and after the arrow has maintained here the overall charge is zero so here the overall charge has to be zero if this is plus one here needs to be - on oxygen gains two electrons so it's going to be oxygen with a negative charge because we have more electrons than protons and then the charge is going to be killed - next one aluminum is losing three electrons so we are going to have more protons and electrons so the charge is going to be positive 3 plus valued positive charts that we have that means that in the ion we have more protons and electrons so it is losing two electrons ion's and the periodic table how can we predict the charge from the periodic table remember what we said metals lose electrons and they're forming ions with positive charge no matters gain electrons so they formed anions negatively charged species metals we see them with positive charge nonmetals we see them with negative charge because they gain electrons because they lose electrons so elements of the year at the one a column of the periodic table have to us one charge elements of the two a of the column of the periodic table two plus charge three a three plus charge and then here they gain electrons right because we have the nonmetals might begin one they gain to the game three so charge - one - two - three let's go from the beginning methods again sorry methods positive charge lose electrons +1 +2 +3 nonmetals gain electrons - 1 - 2 - 3 transition elements the troublemakers of the periodic table they have multiple charges you are not responsible for the charges of the transition elements but you are responsible for the charges of the main elements noble gases not charge they they do not lose they do not gain electron they are stable us they are how it sends - wanna call them 6a - 2 : 5 a - 3 it gains three electrons and then we have the last one it has lost one electron +2 and +3 an exercise here take your time to completely stable basically you have to give the symbol we are dealing with ions the symbol the number of protons the number of elect the number of neutrons the number of electrons as well as the mass number here is the charge take a couple of minutes and come back welcome back let's focus on the first ion that we have here the charge is 3 + so from here we can calculate a number of protons the number of protons we are going to have 3 more protons and the number of electrons we have 2 ND 3 so this is going to be 26 number of neutrons well we know the mass number so we can calculate our of protons so we can calculate the number of neutrons is the difference between this door 58-26 is equal to 32 the symbol we will need to go at a periodic table to figure out which element we have to end the 6 protons here it is so I on 26 protons must number 58 and the charge next one we know the number of protons we know the number of neutrons we can calculate a mass number the sum of this two we know the number of protons we have been given the number of electrons we can calculate the charge C we have four more protons than the number of electrons so the charge is going to be positive four now for the protons let's go at the periodic table zirconium forty protons 91 is the mass number charge plus four number of protons will know the number of electrons and we know the charge it's a negative that means that we have more electrons than protons by three so this one here is going to be fifteen the number of neutrons well it's going to be the difference between the mass number and the atomic number or the number of protons seventeen based on the number of protons we can find the symbol it is phosphorus so phosphorus atomic number fifteen mass number thirty-two charge three minus next one we know the number of neutrons we know the mass number so we can calculate this one here is the difference between the two twenty-six number of protons twenty-six number of electrons 24 so the charge is going to be positive to the blush knowing the number of protons twenty-six we can find the element it's iron IRA 26:56 is the mass number the charge is plus though here we go atomic mass that's what we are using in order to determine to determine that mass of an atom it's called a mass spectrometer here basically we are injecting the sample we are injecting the element from here and we read the results from the screen let's consider that we have naturally-occurring silicon and we inject it into the instrument that's what we say basically we had three isotopes for silicon silicon 28 with silicon 29 and the silicon 30 these on this axis we are getting the percent of adults the silicon 28 has a percent of others of 92 point 23 the silicon 29 has a percent abundance of four point 67 percent and then the silicon 30 has a percent abundance of 3.10 let's make a table reserved with isotopes this is the natural abundance and this is the mass for the silicon 28 the mass is roughly 28 oxidase twenty seven point nine two seven six nine three four the silicon 29 the mass is roughly 29 in fact it's a little less than 29 28 point 97 6495 and then mass for the silicon 30x 29.97 3770 the masses that we have here we call them isotopic mass since they are the mass that we have for its isotope so the isotopic mass for silicon-28 is this the show topic mass for silicon 29 space and the atomic mass for the silicon 30 is this however when we are working in the lab with silicon we do not use any particular isotope we are using the mixture of this three with this razor here 92 4 and 3 or whatever the numbers are so which mass are we going to use well we are not going to use any of these isotopic masses in fact we are going to use the weighted average the weighted average is what we call atomic mass of silicon and the weighted mass in order to calculate the weighted mass in order to calculate the atomic mass we take this times this this times this base times this here it is the sum over 100 and that gives us 28 point zero nine and that's what we are using as mass of silicon in the lab the weighted average the atomic mass can be seen in the periodic table do you remember in the periodic table we have all elements we have boxes its element has a box above the element we have the atomic number and underneath that we have the atomic mass for the element so the number that we see here is not anything else other than the weighted average of all isotopic masses let's say an example rubidium has to naturally recurring I suppose rubidium 8 is 5 and rubidium 87 the mass per guru bidam 85 is eighty four point nine one one eight am you and bad for the eighty seven is eighty six nine zero nine two am you the natural abundance for the 85 isotope is seventy two point 17 and that for the 87 is plenty seven point eight eighty three percent we have to calculate the atomic mass of the rubidium let's make the table that we made there here this is the first isotope this is the second isotope this is the percent ibadis for each line and this is the isotopic mass for each one so let me introduce the data in a different way in one hundred rubidium atoms seventy-two have that mass and two nd8 have that mass so in order to calculate the weighted average I'm going to take this number multiplied by base and this number multiplied by base and then divided by 100 here they carry out the calculations that's a much another one example couple why have the we have the atomic mass isotopes 63 and 65 that's the mass for the 63 that's the mass for the 65 we have to calculate the percent abundance this is the table let's say that this one here the percent abundance for every 63 is a what is for this one here well if this is 2 nd this is editing if this is 40 this is 60 so if this is a this is going to be 100 minus a let's set up the equation that we had earlier this x rays base x weighs over 100 we have this number here we know the atomic mass they gave it to us so we have only one unknown a the percent of buttons for the sixty-three if we know way we can calculate the 100 minus a the percent abundance for the 65 so so I multiply 100 times this here the days and now I multiply sixty four point ninety three times 100 times minus a here and here I take the 100 times sixty four point ninety three and they bring me to the other side after the multiplication it becomes six thousand four hundred and ninety three and this one here becomes 6355 because this one here goes at the other side it has a negative sign and then from here I have a parenthesis 62 93 minus 64 93 Heritage the difference between this two is minus 138 MUO and the difference between this two is minus two so a has no units and it's 69% so this one here it's going to be 100 minus 69 31% for the copper 65 isotope basically we have so we are putting together the same equation the unknown is not here anymore at the atomic mass but it's somewhere here basically at the percent abundance similarly they will have giving us their percent abundance and ask for one of the bluest atomic masses it will have been any any more difficult at this point we have finished chapter four B Part B we discuss about the periodic table we discussed the groups and periods of the periodic table we discuss about the main elements and the transition elements we discuss about the metals metalloids and nonmetals and about the important groups that we have in the periodic table we spoke about ions and we said how and we discuss how we can create ions by adding or removing electrons we spoke about ionization equations and we spoke how can predict charges four main elements from the periodic table at the end of this unit we spoke about atomic mass and how we can calculate atomic mass at this point we have finished with chapter 4 I will see you with chapter 5 thank you very much