Chemical formulasChemical formulas

The secret language of chemists.The secret language of chemists.

DefinitionsDefinitions

Cation – positively charged ion (all metals Cation – positively charged ion (all metals form cations)form cations)

Anion – negatively charged ion (non-Anion – negatively charged ion (non-metals form anions)metals form anions)

Polyatomic ion – an ion (usually negative) Polyatomic ion – an ion (usually negative) that has more than one atom. that has more than one atom.

Ex NOEx NO33--, OH, OH--

Rules for ionic formulasRules for ionic formulas

Ex. NaClEx. NaCl HH22OO CaOCaO

The cation is written first, then the anion.The cation is written first, then the anion.All compounds are neutral so the sum of All compounds are neutral so the sum of

the charges must be zero.the charges must be zero.Subscripts indicate the number of that Subscripts indicate the number of that

atom present in the compound.atom present in the compound.Formulas are written with subscripts that Formulas are written with subscripts that

have the smallest whole number ratio.have the smallest whole number ratio.

Naming acidsNaming acids

Acids are compounds that are capable of Acids are compounds that are capable of producing an H+ ion when they break producing an H+ ion when they break apart.apart.

There are two types of acid – those which There are two types of acid – those which contain oxygen and those that do not.contain oxygen and those that do not.

Acids that do not contain oxygenAcids that do not contain oxygen

Acids that do not contain oxygen are made Acids that do not contain oxygen are made of hydrogen and one other element. of hydrogen and one other element.

HClHCl HFHFTo name these acids, write the prefix To name these acids, write the prefix

hydro- followed by the root name of the hydro- followed by the root name of the other element, followed by the suffix – ic other element, followed by the suffix – ic acid.acid.

Hydrochloric acidHydrochloric acid hydrofluoric acidhydrofluoric acid

Acids that contain oxygenAcids that contain oxygen

Acids that contain oxygen are made of Acids that contain oxygen are made of hydrogen and a polyatomic ion. hydrogen and a polyatomic ion.

HH22SOSO44 HNOHNO22

If the polyatomic ion ends with –ate, the If the polyatomic ion ends with –ate, the acid’s name ends with –ic, if the acid’s name ends with –ic, if the polyatomic ends with –ite, then the acid’s polyatomic ends with –ite, then the acid’s name ends with –ous. (atename ends with –ous. (ateic iteic iteous)ous)

SOSO44 is sulfate so it is sulfuric acid is sulfate so it is sulfuric acid NONO22 is nitrite so it is nitrous acid is nitrite so it is nitrous acid

Writing formulas from namesWriting formulas from names

Use the acid name to determine what the Use the acid name to determine what the anion is, and determine the formula anion is, and determine the formula when combined with H+when combined with H+

Sulfuric acidSulfuric acid hydrofluoric acidhydrofluoric acid

HH++ (SO (SO44))2-2- HH++ F F--

HH22SOSO44 HF HF