This chapter focuses on many-electron atoms. The atomic orbitals developed for hydrogenic atoms are used to describe the electronic structure of many-electron atoms by using the building-up principle, a set of rules for predicting the order in which electrons occupy the available energy states, allowing for the repulsion between electrons and the Pauli exclusion principle. The building-up principle accounts for the structure of the periodic table and the variation through it of atomic radii, ionization energies, and electron affinities. One application of this material is to the discussion of an important inorganic contributor to life: zinc. The chapter also looks into the orbital approximation and the role of electron repulsion.
