Chemical formulas
The secret language of chemists.
Definitions
Cation – positively charged ion (all metals
form cations)
 Anion – negatively charged ion (nonmetals form anions)
 Polyatomic ion – an ion (usually negative)
that has more than one atom.
Ex NO3-, OH
Rules for ionic formulas
Ex. NaCl
H2O
CaO
The cation is written first, then the anion.
 All compounds are neutral so the sum of
the charges must be zero.
 Subscripts indicate the number of that
atom present in the compound.
 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.
 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.
 HCl
HF
 To name these acids, write the prefix
hydro- followed by the root name of the
other element, followed by the suffix – ic
acid.
Hydrochloric acid
hydrofluoric acid

Acids that contain oxygen





Acids that contain oxygen are made of
hydrogen and a polyatomic ion.
H2SO4
HNO2
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)
SO4 is sulfate so it is sulfuric acid
NO2 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 acid
hydrofluoric acid
H+ (SO4)2H+ FH2SO4
HF