hello everybody my name is Iman welcome back to my YouTube channel we made it to video 7 in our high yield mcap General chemistry playlist this video is on the quantum mechanical model of atoms part two specifically we're focusing on electron configuration and we're going to explore how the principles of quantum mechanics translates into the Practical arrangement of electrons within an atom now electron configuration refers to the dist distribution of an atom's electrons among the various orbitals and it's a direct consequence of the quantum mechanical principles that we talked about in part one now the specific order in which electrons populate available orbitals is not AR arbitrary it follows established rules that are based on quantum mechanics and these rules are off bous principle the poly Exclusion Principle and Hun's Rule and we're going to cover each one the off bow principle states that electrons fill orbitals starting with the lowest energy level before moving to higher energy levels so for instance the 1s orbital will fill up before the 2s orbital begins to fill and this principle helps to predict the electronic structure of an atom and it's visually represented in the periodic table by the order of the elements now when we talked about out the four quantum numbers in part one um we did not look at how it is arranged visually on the periodic table and actually this depiction of the periodic table is going to be really useful for when we write out electron configuration for atoms because we can sort of read it like a sentence and fill up orbitals in their appropriate order based off of offb principle in order to write the full electron configuration for an atom of Interest with that being said let's talk about poly Exclusion Principle according to the poly Exclusion Principle each orbital can accommodate a maximum of two electrons which must have opposite spins and this principle arises from the quantum mechanical property that no two electrons can have the same set of all four quantum numbers and then last but not least hun R this this states that electrons will fill degenerate orbitals equal energy orbitals first before pairing up that means that if multiple orbitals of the same energy are available an electron will occupy an empty orbital before it pairs up with another electron in the same orbital this behavior is going to minimize electron electron repulsion and it's energetically favorable now electron configuration is The Language by which chemists articulate the arrangement of electrons within an atom's orbital and learning to write electron configuration systematically is a really important skill skill set to have as a chemist as somebody who's studying for the mcap the energy levels of orbitals increase generally with the principal quantum number n but due to electron electron interactions and the shapes of orbitals this order can sometimes be a little more nuanced for example the 3D orbitals are at a higher energy level than the 4S orbitals all right the 3D orbitals are at a higher energy level than the 4S even though four is a larger number than three a simplified order of how you fill is shown here and you can also directly read it from the periodic table of elements now writing the electron configuration of an element is as easy as possible if we can understand here's the caveat the different parts of the periodic table if we can understand that with the element we're interested in writing the electron configuration for we can simply just read it off of the periodic table knowing that in this part of the periodic table we have S orbitals here we have D orbitals here we have P orbitals and here we have F orbitals now we can see this in action by doing a quick example so let's say we are interested in writing the electron configuration for carbon all right let me show you where carbon is on this periodic table I'm going to draw a little dot in the box where carbon would be after I erase all of this carbon would be right here all right this is Carbon on the periodic table now we want to write the electron configuration for carbon based off of what we've learned um so far about our three rules all right so the electron configuration for a carbon we're just going to read it off like a sentence from the periodic table of elements now we filled up 1 S2 all right we filled this up as well 2 S2 and then we've made it here to this 2p part and we land right here so we only make it one two boxes into this 2p region all right and so we filled up 1 S2 2 S2 2 P2 and then we just put together those three components together to write the electron configuration for carbon 1 S2 2s2 2 P2 let me know if you have any questions any comments concerns other than that good luck happy studying and have a beautiful beautiful day future doctors