Electron configuration, continued principles

We might, just accept it as a brute fact about the world that the series of elements was discrete. But if there were a finite number of properties, combinations of which generate the physical possibilities represented by the periodic table, then variation would necessarily be discrete rather than continuous. We can believe in the existence of these fundamental entities and properties without subscribing to any particular account of them (e.g. an account in terms of electronic configuration), such accounts at least show us the way in which chemical properties could be determined by more fundamental ones. The point is that, given the principle of recombination, unless those more fundamental properties exist, unactualized elements would not be physical possibilities (14). 

Strategy (a) Use the building-up principle discussed in Section 2.2 to write the electron configuration with principal quantum number n = 1 and continue upward until all the electrons are accounted for. (b) To determine whether the atom should be classified as a representative element, a transition metal, or a noble gas, consider its electron configuration characteristics, (c) Examine the pairing scheme of the electrons in the outermost shell. The element will be diamagnetic if all electrons are paired and paramagnetic if some are unpaired. 

Strategy Use the Aufbau principle discussed in Section 6.8. Start writing each electron configuration with principal quantum number n = 1, and then continue to assign electrons to orbitals in the order presented in Figure 6.23 until all the electrons have been accounted for. 

We can continue in this manner, building up the configuration of each element by adding a set of quantum numbers for one last electron to the configuration of the element before it This process of adding one electron to those of the preceding element is called the build-up principle. 

---