Standard 2a Preknowledge
2a) Students know how to relate the position of an element in the periodic table to its quantum electron configuration and to its reactivity with other elements in the table.
CALIFORNIA FRAMEWORKS SUMMARY: Each element has a unique electron configuration (also known as quantum electron configuration) that determines the properties of the element. Quantum mechanical calculations predict these electron energy states, which provide the theoretical justification for the organization of the periodic table, previously organized on the basis of chemical properties.
Students can learn the principal quantum numbers—which are 1, 2, 3, 4, 5, 6, and 7—and the corresponding periods, or horizontal rows, on the periodic table. They can learn the angular momentum quantum numbers that give rise to s, p, d, and f subshells of orbitals and the rules for the sequence of orbital filling. The electrons in the highest energy orbitals with the same principal quantum number are the valence electrons. For example, for all elements in Group 1, the valence electron configuration is ns1, where n is the principal quantum number. Analogously, all elements in Group 16 have valence electron configurations of ns2np4. Particular configurations of valence electrons are associated with regular patterns in chemical reactivity. Generally, those elements with one electron in excess or one electron short of a full octet in the highest occupied energy level, the alkali metals and halogens, respectively, are the most reactive.