Rules for Naming Inorganic Compounds



Positive Ions (cations)

Monatomic positive ions take the names of the metal from which they are derived:

IonName
Na+sodium ion
Ca2+calcium ion
Al3+aluminum ion

When a metal forms more than one ion, it is necessary to distinguish between these ions. The accepted practice today is to indicate the charge of the ion by a roman numeral in parenthesis immediately following the name of the metal:
IonName
Fe2+ iron(II)
Fe3+iron(III)
Cu+copper(I)
Cu2+copper(II)
Sn2+tin(II)
Sn4+tin(IV)

Some metals are still referred to using the stem of their Latin name, with -ous and -ic indicating the lower and higher charges, respectively:
IonName
Fe2+ ferrous
Fe3+ferric
Cu+cuprous
Cu2+cupric
Sn2+stannous
Sn4+stannic

The only common inorganic polyatomic positive ions are:
IonName
NH4+ammonium
Hg22+mercury(II) or mercurous

Negative Ions (anions)

Monatomic negative ions are named by adding the suffix -ide to the stem of the name of the nonmetal from which they are derived:
IonName
H-hydride
F-fluoride
Cl-chloride
Br-bromide
I-iodide
O2-oxide
S2-sulfide
Se2-selenide
Te2-telluride
N3-nitride
P3-phosphide
C4-carbide

The nomenclature of polyatomic anions is more complex. The names of the most common are:
IonFormula
borateBO33-
carbonateCO32-
hydrogen carbonate (bicarbonate)HCO3-
hypochloriteClO-
chloriteClO2-
chlorateClO3-
perchlorateClO4-
chromateCrO42-
dichromateCr2O72-
cyanideCN-
phosphitePO33-
phosphatePO43-
hydrogen phosphateHPO42-
dihydrogen phosphateH2PO4-
hydrogen sulfite (bisulfite)HSO3-
hydrogen sulfate (bisulfate)HSO4-
sulfiteSO32-
sulfateSO42-
sulfideS2-
hydrosulfideHS-
hydroxideOH-
nitriteNO2-
nitrateNO3-
oxalateC2O42-
permanganateMnO4-
silicateSiO44-

Compounds

For ionic compounds, the name of the positive ion (cation) is given first, followed by the name of the negative ion (anion):
CompoundName
CaCl2calcium chloride
Fe(ClO4)3iron(III) perchlorate
FeBr2iron(II) bromide
NaHCO3sodium hydrogen carbonate
(NH4)2SO4ammonium sulfate

For covalent compounds involving metals, the above practices are still used:
AlCl3aluminum chloride
SnCl4tin(IV) chloride

For compounds made up of nonmetals, the first element named is the one with lower electronegativity, with the second having the higher electronegativity:
CompoundName
HClhydrogen chloride
H2Shydrogen sulfide
NF3nitrogen fluoride

If more than one binary compound is formed by a pair of nonmetals, the Greek prefixes di (two), tri (three), tetra (four), penta (five), hexa (six), etc. are used to designate the number of atoms present. The mono- prefix is rarely used.
CompoundName
N2O5dinitrogen pentoxide*
N2O4dinitrogen tetroxide
N2O3dinitrogen trioxide
N2O2 dinitrogen dioxide
N2Odinitrogen oxide
NO2nitrogen dioxide
NOnitrogen oxide

*when immediately followed by a vowel, the a is dropped.

Many of the most common binary nonmetal componds have common names which are use more frequently:

CompoundName
H2Owater
H2O2hydrogen peroxide
NH3ammonia
N2H2hydrazine
PH3phosphine
AsH3arsine
NOnitric oxide
N2O nitrous oxide

Acids

The names of inorganic oxyacids (those that contain oxygen) are derived from the names of the polyatomic ions, replacing -ite with -ous, and -ate with -ic:

HClOhypochlorous acidHClO2chlorous acid
HClO3chloric acidHClO4perchloric acid
HNO2nitrous acidHNO3nitric acid
H2SO3sulfurous acidH2SO4sulfuric acid
H3PO3phosphorous acidH3PO4phosphoric acid
H2CO3carbonic acidH2CrO4chromic acid
H2C2O4oxalic acidH3BO3boric acid
HMnO4permanganic acidH4SiO4silicic acid

Other common acids include*:

HClhydrochloric acidHFhydrofluoric acid
HIhydroiodic acidHBrhydrobromic acid

*Acids which do not contain oxygen derive their name from the nonmetal ion or polyatomic ion with a hydro- prefix. The -ide suffix for the anion is replaced with -ic.

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