One of the biggest topics in the teaching and learning of chemistry is the use of the aufbau principle to predict the electronic configurations of atoms and to explain the periodic table of the elements. This method has been taught dunia forex many generations of students and is a favorite among instructors and textbooks when it comes to setting questions. Whatever the cause there is no excuse for perpetuating this educational myth as I will try to explain. The next ingredient is a knowledge of the atomic orbitals into which the electrons are progressively placed in an attempt to reproduce the natural sequence of electrons in atoms that occur in the real world.
Oddly enough these orbitals, at least in their simplest form, nowadays come from solving the Schrödinger equation for the hydrogen atom but let’s not get too sidetracked for the moment. The different atomic orbitals come in various kinds that are distinguished by labels such as s, p, d and f. Each shell of electrons can be broken down into various orbitals and as we move away from the nucleus each shell contains a progressively larger number of kinds of orbitals. Fourth shell contains 4s, 4p, 4d and 4f orbitals and so on. The next part is that one needs to know how many of these orbitals occur in each shell. As a result there are potentially one s orbital, three p orbitals, five d orbitals, seven f orbitals and so on for each shell.
Now comes the magic ingredient which claims to predict the order of filling of these orbitals and here is where the fallacy lurks. Rather than filling the shells around the nucleus in a simple sequential sequence, where each shell must fill completely before moving onto the next shell, we are told that the correct procedure is more complicated. And this is finally the point at which the aufbau diagram, which I am going to claim lies at the heart of the trouble, is trotted out. The order of filling is said to be obtained by starting at the top of the diagram and following the arrows pointing downwards and towards the left-hand margin of this diagram. This recipe when combined with a knowledge of how many electrons can be accommodated in each kind of orbital and the number of such available orbital in each shell is now supposed to give us a prediction of the complete electronic configuration of all but about 20 atoms in which further irregularities occur, such as the cases of chromium and copper. Again I don’t want to get side-tracked and so will concentrate on one of the far more numerous regular configurations.