okay this is the american chemical society study guide and i'm going to be reviewing uh the sixth chapter atomic structure and we're gonna be looking at practice questions so in all neutral atoms there are equal numbers of and the key in this question is neutral so neutral atoms need to have to be the same number of positives and the same number as negatives our protons are positive our electrons are negative so that is d which element is represented by x with 56 as the mass number and 24 as the atomic number so the atomic number z is going to give us the number of protons and this is equal to 24. so looking at the periodic table i can tell that this is chromium cr answer d which statement concerning the structure of the atom is correct so remember that protons and neutrons are in a very very very small compact [Music] massive so meaning it has most mass and then the electrons are way out here they're very light so they don't have much mass but they have a lot of volume so d is the correct answer protons and neutrons have most of the mass that occupy very little of the atom so the answer here is also d question number four the number of neutrons okay again remember we have our mass number our mass number a and this is equal to the number of neutrons plus the number of protons and then we have z which is equal to the number of protons so i can take 37 and subtract 17 and i get 20 for the number of neutrons and that is letter b it says number five an argon atom is isoelectronic so iso means same electronic we're looking for the electron configuration or another way to put this is the same same clean that up number of electrons okay so an argon atom argon so argon has if you look at the periodic table argon has um protons equal to 18 and that means that our electrons are going to equal to 18. so we want to pick the same one one of these that has the same number of electrons so ti4 plus if i look at ti4 plus titanium has 22 protons um and then that four plus means that it has lost four electrons 9 minus 4 electron this gives me 18 electrons and this is the same as argon so that is why the answer is c so if you're to try to do this remember that um if you're going to have something that's isoelectronic with a noble gas um that species is going to be an ion only argon as a neutral atom can be isoelectronic with argon okay so just in terms of like giving yourself some spare time here and doing the problem just ignore a and b and then answer the question for c and d says which pair of particles has the same number of electrons again we're looking for iso electronic and if you look at chlorine f minus minus one minus um fluorine has nine protons um and if it's going to have a negative charge on it it will have 10 electrons so that's what gives it its minus one charge magnesium two plus has 12 uh protons and that's lost two electrons so minus two proton electrons out of 12 that would give me 10 electrons overall so these have the same number of electrons so the answer is a and so you would have to do this for each of these species just notice that you could just cross out some of these because they um they can't have the same number of electrons they're neutral atoms it says which ion has 26 electrons so again we're looking for something that would have um uh like a certain number of protons so we have to look at how many protons it has and then it could have 26 electrons if it had 26 protons and it was neutral that could be one of them but these are not it's neutral okay so they have to have more or less um electrons they're all positive all plus two so really what we're looking for if we're going to have 26 electrons would be um an ion with 28 protons so 28 positives minus 2 electrons gives me 26 electrons and that is here nickel so nickel has 28 positive charges and since it has a two plus charge it has lost two electrons and that gives me 26 electrons overall says which statement is true the nucleus of an atom contains neutrons and an electron no so we're going to go back to that picture that i had protons and neutrons are in the nucleus and the electrons are way out here okay way out here and the electrons have the volume and the small nucleus has the mass so um the atomic number z is the number of protons in one atom i've been uh looking at already so the atomic number of an element is the number of protons in one atom we've talked about this and this is z okay this is z so question number nine is how does um an atom of magnesium differ from a magnesium ion these are going to be different from the number of electrons um the numbers electrons are going to differ in an ion the number of protons are the same so it can't have anything to do with protons being the same um the number of neutrons in an ion um if they have different number of neutrons they're not ion they're isotopes so the ion has an inert gas electron configuration the atom does not so just a quick review mg2 plus has 10 electrons and this is the same as neon okay this is a so very similar question question 10 the sodium ion and the sodium atom these are going to differ in the number of electrons that they have and it turns out that it has fewer electrons and here's how we know this so sodium has 11 protons and 11 electrons sodium ion and na plus remember this is group one so everything in group one has a plus one charge it loses one electron so it has ten protons and sorry ten electrons i'll start out eleven protons and 10 electrons there we go it has fewer electrons so a as well so which term best characterize the relations of hydrogen to deuterium so hydrogen is h11 deuterium is h12 so these are isotopes um hydrogen atom has one proton no neutrons deuterium has one proton and one neutron isotopes of each other see there's also something called tritium this is very radioactive and is a byproduct of nuclear fission so it's also another isotope all right question number 12. it says um element x occurs naturally to the extent of twenty percent in eighty percent of thirteen the atomic mass is nearest two so you have to use the equation where you multiply the mass abundance in terms of a decimal place so i took 20 and i divided through by 100 i did the same thing for 80. and i'm multiplying by the amu's so this is 12 atomic mass units right this is my mass number a then i'm going to add to it 0.80 times 13 13 amuse and i get 12.8 amu's and this is closest to c all right question 13. um we're looking for something isoelectronic and isotopic so isoelectronic is same number of electrons isotopic is different number of neutrons and for both of these they'll have the same number of protons so we're going to have to look for something that is going to have the same number of protons in here and these these don't work okay they don't have the same number i'm sorry excuse me the same number of electrons so isoelectronic has same number of electrons um these are isotopic because um a is 39 for the first one and a is 40 for the second one and so this means that these have different number of neutrons but k plus they both have the same number of protons and the same number of electrons this is an element in question 14 an atom of an element of atomic number 84 so atomic number remember a i'm sorry excuse me z z equals 84. math number a equals 199. oh sorry guys we're not doing this question in chem 1a um you'll get to this is nuclear chemistry so question 14 and then question 15 are um later chem 1b um so let's move on to another chem 1a question which is 16. um millikin's experiment so milk and confirmed the magnitude of the charge on an electron this is c and let's see valence electron configuration so we're looking for the outermost configuration for an element in period five and group three a so we have to look on the periodic table and find out what this element is this turns out to be indium and it's valence electron configuration let me just write down its abbreviated configuration is kr 5s2 4d10 5p1 and then the valence electrons are going to be these ones here in the outermost shell so we're looking for 5s2 5p1 and that's on the next page i think did i skip it yes i did it's right here sorry on this page okay question number 18. an impossible electron configuration one of the ways to remember electron configurations is using the periodic table or 1s 2s 2p 3s 3p 3d and you can go like this right that can be helpful if you're looking for something um for question number for question b here you can tell that this is impossible but because if you notice there's no two d's and that's because l is equal to zero all the way up to n minus 1 and then m sub l equals negative l all the way to plus l so there's no such thing as a 2d at all so this is the impossible electron configuration all right question number 19 ground state electronic configuration of manganese m n so m n has um z equals 25. so there's two different ways to write this um i'm going to write it this way 1s2 2s2 2p6 that's 10 electrons moving on to the next period 3s2 3p6 and then you'll notice you go down to the 4s's 4s2 and 3d5 and it's okay to change places with these um that's what's happening here in letter d okay they just put the three in front they just change places and that's fine there are multiple ways to represent electron configurations and if you remember off valve's principle doesn't always work once you get into the transition metals uh question 20 which species has this ground state electron configuration rearrangement so let me add up the number of electrons so the number of electrons is 26 electrons and that would be um d and the other thing to note about this is note that in this one um there's no 4s2 electrons and that's because these are lost those are the valence and that means you have a positive ion so um notice that these have positive ions okay question number 21 is the maximum number of electrons it can occupy labeled dxy remember that any orbital um can hold only two electrons right because we have the up and the down now the d's there are five possible d orbitals and the dx y happens to be one of them and it can only hold a maximum of two electrons okay an atom of iron has two electrons and six 3d electrons okay and lost my periodic table there an atom of iron has two electrons and six three d electrons how many unpaired electrons would there be in f2 plus so um i like to use the orbital diagram for this so the 4s2 and then the 3d and we go one one two three four five six three d six so one one two three four five so um i always like to start with the atom and then work to the ion one two three four five and six and then it says um how many unpaired electrons are going to be in the fe2 plus so what i'm gonna do is i'm gonna take um these two electrons away and um we're gonna find is that these are the valence electrons remember that because it's um n equals four those are lost first so in the fe two plus um i would have a total of six um electrons in the 3d which gives me four unpaired electrons in the fe2 plus that's also the same for se so for question number 23 um you can just do the same thing that i did you don't need to use molecular orbital theory but remember that in molecular orbital uh theory um the definition for paramagnetic is on electrons that means that they will be responsive to a magnetic field unpaired electrons so that's what i'm looking for and i'm just basically looking for the same thing that i just did in the question before i answer i showed you this one so let's um let's also look at the zinc what does the zinc look like well unfortunately zinc everything's paired because this is 3d 10. and then let's look at ti4 plus so ti4 plus ti4 plus loses the 3d twos and the sorry the four s twos and the three d twos it loses all those so that can't work so we know that this has to be a um again looking at question number 22 we could see that iron 2 plus is paramagnetic only that's the only one that is okay and 24 it says which one of these electron diagrams could represent the ground state of the p valence electrons and carbon so dc cannot you can never have electrons pairing both spin up in the same orbital that violates paulie's exclusion principle a violates um the hund's rule or sometimes called the bus law so it can't be that one um and when uh we draw our orbital diagrams we always by convention draw up up so that leaves us with d um you know b is a possibility but that's not the way that we draw our electrons when we draw orbital diagrams we follow all of the rules and then we by convention draw up up okay in 25 the existence of quantized energy levels lots of experiments that we talked about um one of the experiments that we talked about was atomic lime spectra d in terms of the experiments of the photoelectric effect um that really showed that photons were quantized not that electronic levels and energy levels were quantized the atomic line spectra remember we looked at rydberg's equation and the line spectra of hydrogen okay for question number 26 we're looking for highest frequency remember that e equals h nu so if you increase your frequency you're increasing your energy and if we're looking at these as n equals one n equals two n equals three and remember also this is a mission so emission is going from high n to low n um and you want the biggest gap so the biggest gap was um in this example 3 to 1 is bigger than n equals 4 because remember these gaps get really small right this energy increases as one over n squared proportional to one over n squared so three to one is bigger than four to two and then the other option seven to five is super small ten to eight is super small so really the biggest one is going to be this one right here which is a okay question number 27 if n equals 4 l can be 0 one two or three and then m sub l can be for any of these remember this could be zero this could be negative one zero one this could be negative two negative one 0 1 2 this could be negative 3 negative 2 negative 1 0 1 2 and 3. so um in terms of which orbitals these are this is the s this is the p this is the d this is the f and we see um the number of s's is always one p's is three these is five s is seven so with quantum number four we could have something of l equals three right we could have something of m sub l equals minus three but we cannot have something of m sub s equal to one so that means the correct answer is a all right question 28 when an atom of an electropositive atom becomes an ion so in this case we have electropositive um an atom of an electropositive atom becomes an ion so electropositive means that um you're talking about metals so remember electronegative means that um you have in a bond electrons pull towards self okay um so you have a high z effective the effective right is the effective um but in question number 28 these don't gain electrons nope they don't become larger they don't emit we're not talking about nuclear reactivity it's none of these okay so this is ghee um in question number 29 the orbitals of the t2p so all of the p orbitals we typically represent like this um as you get higher n you have more nodes but in this n equals two then you have a dumbbell shape see um if you have the um uh helium um has two electrons in the 1s so 1s2 um when it becomes singly ionized becomes 1s1 plus 1 electron so in this one electron you're going to have a similar um spectrum to hydrogen um yep that's true the remaining electron is not easier to remove it's always harder to remove the nuclear charge does not change and it has not lost any mass so it is a and that's it