One of the triumphs of quantum mechanics was the successful explanation of the arrangement of electrons in atoms and the structure of the periodic table. Now that we have seen (Chapter 8) how the table is based on electronic structure, we can present an overview of the chemical elements that make up our universe. This is the full deck with which the game of chemistry is played. This chapter will be a wrap-up of the ideas presented in the first nine chapters.

The rows or periods of different length in the table represent the filling of different orbitals: s in Row 1; s + p in Rows 2 and 3; s + d + p in Rows 4 and 5; and s + f + d + p in Rows 6 and 7. The fully developed table from Chapter 8 is shown in the right margin, with the representative elements (filling of s and p orbitals), transition metals (d orbitals), and inner transition metals (f orbitals) differentiated by color. Each period begins with the occupancy of a new s orbital and (after Row 1) ends with a noble gas with a closed s + p electron shell. The representative elements are divided vertically into eight groups, labeled IA through VIIA, and 0 for the noble gases. The Roman numeral in the group number indicates the number of s and p electrons in the outer shell.