Name binary covalent compounds using numerical prefixes, name common binary and oxyacids, and review the semester's bonding and nomenclature skills.
Covalent (molecular) compounds are named differently from ionic ones, since there is no fixed charge-balancing rule to determine the ratio -- so the name simply states it directly using Greek numerical prefixes: mono- (1, skipped on the first element only), di- (2), tri- (3), tetra- (4), penta- (5), hexa- (6), hepta- (7), octa- (8), nona- (9), and deca- (10). CO2 is carbon dioxide; SO3 is sulfur trioxide; N2O4 is dinitrogen tetroxide. When a prefix ending in "a" or "o" would collide with the vowel that starts "oxide," the prefix drops its final vowel for smoother pronunciation -- "tetra" + "oxide" becomes "tetroxide," and "mono" + "oxide" becomes "monoxide," as in carbon monoxide, CO.
Acids are named based on the negative ion left behind once the acidic hydrogen is removed. A binary acid (hydrogen plus one other nonmetal, with no oxygen) is named "hydro-" plus the nonmetal's root plus "-ic acid": HCl is hydrochloric acid, and H2S is hydrosulfuric acid. An oxyacid (hydrogen plus a polyatomic ion containing oxygen) is named directly from that polyatomic ion's name: an "-ate" ion becomes an "-ic acid" (sulfate becomes sulfuric acid, H2SO4; nitrate becomes nitric acid, HNO3), while an "-ite" ion becomes an "-ous acid" (sulfite becomes sulfurous acid, H2SO3; nitrite becomes nitrous acid, HNO2).
This is also a checkpoint week: the first half of this course built the toolkit -- matter and measurement, the atom and its history, electron configuration, the periodic table and its trends, three types of bonding, and now naming compounds of every kind. Everything from here forward (the mole, reactions, stoichiometry, gases, solutions, acids and bases, thermochemistry) is built directly on top of these first eighteen weeks, so this is a genuinely good week to make sure every piece is solid before building further.
Mastery looks like: They correctly name binary covalent compounds and common acids, and can explain why ionic and covalent compounds require two different naming systems.
Common stumbles: Using "mono-" on the first element in a covalent name (it is only ever used on the second element); mixing up "-ic" and "-ous" acid endings relative to "-ate" and "-ite" polyatomic ions.