Periodic Table and Electronic Configuration

Historically, Mendeleev built his periodic table purely from the empirically-observed periodicity of elemental properties, without any knowledge of atomic structure, by arranging elements in increasing order of atomic mass. It was only later, with the arrival of the quantum mechanical model of the atom, that these properties could be correlated to electronic configuration. As covered in the previous chapter, electrons in an atom are distributed among shells and subshells according to the Aufbau principle (filling in order of increasing orbital energy), Pauli's exclusion principle, and Hund's rule of maximum multiplicity. When elements are arranged in increasing order of atomic number Z, their electronic configuration shows a periodicity that directly produces the characteristic row-and-column structure of the modern periodic table — in fact, an element's exact position in the table is correlated with the quantum numbers of its last-filled orbital. The next three subsection …