hello and welcome to the chemistry solution this tutorial is on effective nuclear charge although negatively charged electrons and atoms are attracted to the positively charged nucleus there at the same time repelled by other electrons in the atom and so the effective nuclear charge is the average nuclear charge felt by an individual electron in an atom taking into consideration the shielding effect of inner shell electrons and we'll explore in more detail what that means as we go through this tutorial the effective charge is equal to Z minus s where Z is the number of protons in the nucleus and s is the number of inner shell electrons now remember the number of protons in the nucleus is the same as the atomic number and can be easily determined by using your periodic table in this tutorial we'll go through how to determine the number of inner shell electrons let's look at an example what is the effective nuclear charge felt by an electron in the N equals 3 shell of sulphur remember that the effective charged is equal to the number of protons in the nucleus minus the number of inner shell electrons the atomic number of sulphur is 16 and that means sulphur has 16 protons in the nucleus now let's start diagramming the electrons around the nucleus of sulphur remember that for a neutral atom the number of electrons is equal to the number of protons and so a neutral sulphur atom has 16 electrons remember that the N equals 1 shell of sulphur can hold two electrons we now need to place 14 more electrons around the nucleus of sulphur the N equals 2 shell can hold 8 electrons so now we've diagrammed 10 electrons the N equals 3 shell can hold 14 electrons total but because sulphur only has 16 electrons and we've already diagrammed 10 of them there will only be 6 electrons remaining to put into the N equals 3 shell now the question is asking us what the effective nuclear charge is felt by an electron in the N equals 3 shell that means that both the N equals 2 and N equals 1 shells are inner shells and so the number of inner shell electrons is equal to 10 this makes the effective charge for an electron in the N equals 3 shell of sulfur equal to 6 now whenever you are looking for the effective nuclear charge felt by an electron in the outermost shell of an atom and in Sulphur the outermost shell is the N equals 3 shell the effective charge will always be equal to the group number on the periodic table but in some cases you'll be asked to find the effective charge for an electron not in the outermost shell so let's go through how we would do that and we're going to use pretty much the same method what is the effective nuclear charge felt by an electron in the N equals 2 shell of chlorine a neutral chlorine atom has 17 protons and 17 electrons for this example I'm going to show you another way to diagram out the electrons so you don't have to draw an elaborate picture each time remember that the N equals 1 shell can hold two electrons the N equals 2 shell can hold 8 electrons so now we have 7 electrons left 17 minus 8 minus 2 that means in the N equals 3 shell there will be 7 electrons even though total N equals 3 shell could hold 14 now remember that Z is equal to the atomic number of chlorine which is equal to the number of protons which is 17 and s is the number of inner shell electrons remember that the inner shells are between the shell of interest and the nucleus of the atom and in this case because we're looking for the effective nuclear charge fault by an electron in the N equals 2 shell the only inner shell electrons will be in the N equals 1 shell and there are only two of them this means that the effective nuclear charge felt by an electron in the N equals 2 shell of chlorine is equal to 15 thanks for watching the chemistry solution we hope you enjoyed this tutorial you