Nearly everyone who teaches introductory chemistry courses, whether in secondary schools or in universities, makes the connection between the periodic table and electronic configurations. Eric Scerri provides history and science that can make the discussion of that topic both more historically and scientifically accurate. It is appropriate that this subject should receive renewed attention, because this year is the hundredth anniversary of J. J. Thompson's discovery of the electron. The great physicist also had a strong interest in chemistry, and it was the discoverer of the electron himself who first proposed that arrangements of this new particle in atoms could explain their periodically recurring properties. While recounting the history of electronic configuration theories and periodicity, Scerri emphasizes the limitations of electronic configurations in "explaining" periodicity and he also illustrates several alternative ways of showing the periodic table, each of which has an advantage over the conventional display.