Noble gas periods of the periodic table, the noble gases are exactly the members of group 18. Noble gases are typically highly unreactive except when under particular extreme conditions. The inertness of noble gases makes them very suitable in applications where reactions are not wanted. For example, argon is used in incandescent lamps to prevent the hot tungsten filament from oxidizing; also, helium is used in breathing gas by deep-sea divers to prevent oxygen, nitrogen and carbon dioxide (hypercapnia) toxicity. The properties of the noble gases can be well explained by modern theories of atomic structure: their outer shell of valence electrons
Copia: Foundations of the Abundant Style on Quintillian's rhetorical guide, "Institutio Oratoria". The first chapter of book 10 in Quintillian's "Oratoria" is titled ""De copia verborum"". This is quite possibly where Erasmus received his most direct inspiration for the book. In that 10th chapter, Quintillian declined to give examples for employing the abundant style, on the grounds that each individual case requires a unique solution. This left the door open for Erasmus to detail the abundant style in "Copia". Erasmus acknowledges Quintillian in the preface, and borrows from him (and other classical authors) throughout "Copia", sometimes citing, sometimes not. As further revisions of "Copia" are printed,