the first thing we need to do to find electron configurations is to find the number of electrons for the element so we can find this on the periodic table and we're going to look at the number above the element symbol which is called the atomic number that'll tell us the number of protons but it also tells us the number of electrons and we can use that number as we try to find the electron configuration for whatever element we're interested in so we'll move helium over to group 2 since it fits better there for electron configurations we have our periodic table and we just need to memorize that everything every element in group 1 ends in s1 group 2 ends in s2 we'll go over to the p block those elements in group 3 they end in the p1 and then p2 all the way up to p6 going back to the transition metals we start with d1 and go all the way to d10 for boron we'll look first at row or period one on the periodic table we can see that the hydrogen has atomic number one it is in row one so we're going to write one down that's the period it's also the energy level for the orbital that we're talking about then we'll go to number two which ends in s2 so we're going to call the first part 1s2 and then we're done with period one we'll go to period two and we see that lithium atomic number three that ends in s1 next beryllium that ends in s2 and those are all of the s's in that second period or energy level so we're going to put 2s and since there are two electrons there two now we're going over to the p block and we're at boron which is the element we're writing the configuration for and we can see that boron ends in p1 now we're still in the second period so it's going to be a 2p and boron ends in one so that's it that's the electron configuration for boron we'll do chlorine the same way we did boron in rho or period one we can see with hydrogen we'll start atomic number one we have the one s one and one s two full so we just write one s two we go across and we're actually back in row or period two so we have lithium and beryllium 2s 2 that's full we go over to the p block and we have all of that full p1 through p6 so we just need to write 2p 6 we go down to row 3 we have 3s1 and 3s2 those are full so we write 3s2 we're back over across to the p block and we can see chlorine's there at p5 so we're almost there so we put 3p and since chlorine's in the p5 group 3p5 that's the electron configuration for chlorine we'll try one more vanadium so vanadium has atomic number 23 so we have 23 electrons and we're going to go through the periodic table until we get to vanadium so we'll start in period one there with hydrogen atomic number one and we see the 1s1 and 1s2 those are full so we'll write 1s2 now we move down to the second period we have the 2s1 and 2s2 those are full then we go across we're into the two ps and all of the p's are full so we'll put 2p 6 down to period 3 3s 2 then we have all of the 3 p's those are full as well so 3p6 we're down to period 4 and we're getting close to this 23 electrons that we have for vanadium so in period 4 we have 4s1 and 4s2 those are full so we'll write 4s2 and then we're into that d block there and if we go over 1 2 3 that's where vanadium is so we would expect that we would have 4 d 3. however this is the one exception that you need to be aware of if you're using this method when we get to the d block we always take one away from the period number so instead of 4d3 we would have 3d3 is the electron configuration for vanadium so at this point it really becomes just a matter of practicing them do them yourself struggle with them and then look at the answer and go back and do this until you can get them right every time the pattern is pretty much the same for all the elements you just continually add electrons on this is dr b and thanks for watching