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Current time:0:00Total duration:2:31

Worked example: Identifying an element from successive ionization energies

AP.Chem:
SAP‑1 (EU)
,
SAP‑1.A (LO)
,
SAP‑1.A.4 (EK)
,
SAP‑2 (EU)
,
SAP‑2.A (LO)
,
SAP‑2.A.2 (EK)
,
SAP‑2.A.3 (EK)

Video transcript

we are told that the first five ionization energies for a third period element are shown below what is the identity of the element so pause this video and see if you can figure it out on your own and it'll probably be handy to have a periodic table of elements so before I even look at a periodic table of elements let's make sure we understand what this table is telling us this is telling us that if we start with a neutral atom of this mystery element it would take 578 kilojoules per mole to remove that first electron to turn that atom into an ion with a +1 positive charge and then it would take another 1817 kilojoules per mole to remove a second electron so to make that ion even more positive and then after that it would take another 2745 kilojoules per mole to remove the third electron and then to remove the fourth electron it takes away larger amount of energy it takes 11,000 578 kilojoules per mole and then the fifth electron takes even more 14,000 842 kilojoules per mole and so for the first second and third you do have an increase in ionization energy but when you go to the fourth the energy required to remove those is way higher so to me these look like you're removing valence electrons and these look like you're removing core electrons so one way to think about it is let's look on our periodic table of elements and look for a third period element that has three valence electrons so we have our periodic table of elements we want a third period element so it's going to be in this third row and which of these has three valence electrons well sodium has one valence electron magnesium has two valence electrons aluminum has three valence electrons so one way to think about it is that first electron but it's a reasonable ionization energy then the second one little higher than the third a little bit higher than after that but then the fourth you're starting to go into the core you're going to take an electron out of that full second energy shell which takes a lot of energy and so this is pretty clearly a lumen 'm that is being described