Chemical formulas The secret language of chemists.

Definitions Cation – positively charged ion (all metals form cations) Cation – positively charged ion (all metals form cations) Anion – negatively charged ion (non- metals form anions) Anion – negatively charged ion (non- metals form anions) Polyatomic ion – an ion (usually negative) that has more than one atom. Polyatomic ion – an ion (usually negative) that has more than one atom. Ex NO 3 -, OH -

Rules for ionic formulas Ex. NaClH 2 OCaO The cation is written first, then the anion. The cation is written first, then the anion. All compounds are neutral so the sum of the charges must be zero. All compounds are neutral so the sum of the charges must be zero. Subscripts indicate the number of that atom present in the compound. Subscripts indicate the number of that atom present in the compound. Formulas are written with subscripts that have the smallest whole number ratio. Formulas are written with subscripts that have the smallest whole number ratio.

Naming acids Acids are compounds that are capable of producing an H+ ion when they break apart. Acids are compounds that are capable of producing an H+ ion when they break apart. There are two types of acid – those which contain oxygen and those that do not. There are two types of acid – those which contain oxygen and those that do not.

Acids that do not contain oxygen Acids that do not contain oxygen are made of hydrogen and one other element. Acids that do not contain oxygen are made of hydrogen and one other element. HClHF HClHF To name these acids, write the prefix hydro- followed by the root name of the other element, followed by the suffix – ic acid. To name these acids, write the prefix hydro- followed by the root name of the other element, followed by the suffix – ic acid. Hydrochloric acidhydrofluoric acid

Acids that contain oxygen Acids that contain oxygen are made of hydrogen and a polyatomic ion. Acids that contain oxygen are made of hydrogen and a polyatomic ion. H 2 SO 4 HNO 2 H 2 SO 4 HNO 2 If the polyatomic ion ends with –ate, the acid’s name ends with –ic, if the polyatomic ends with –ite, then the acid’s name ends with –ous. (ate  ic ite  ous) If the polyatomic ion ends with –ate, the acid’s name ends with –ic, if the polyatomic ends with –ite, then the acid’s name ends with –ous. (ate  ic ite  ous) SO 4 is sulfate so it is sulfuric acid SO 4 is sulfate so it is sulfuric acid NO 2 is nitrite so it is nitrous acid NO 2 is nitrite so it is nitrous acid

Writing formulas from names Use the acid name to determine what the anion is, and determine the formula when combined with H+ Sulfuric acidhydrofluoric acid H + (SO 4 ) 2- H + F - H 2 SO 4 HF H 2 SO 4 HF