Introduction to Chemical Nomenclature: Inorganic Compounds

There are three types of inorganic nomenclature based on IUPAC:

• Systematic: uses prefixes and some suffixes

• Traditional: uses prefixes and suffixes

• Stock: uses roman numbers

Every name depends on the compound’s nature, it is essential to consider if we have binary compounds (2 elements), ternary compounds (3 elements), or quaternary compounds (4 elements).

Tips to name inorganic compounds:

• When writing the compound, the cation always comes before the anion, for example, FeS, Fe is your cation, and S is your anion.

• When a compound is formed, each element has an oxidation number, when they combine they are going to exchange those oxidation numbers, for example, AlCl3, Aluminum has an oxidation number of 3+ and Cl as an anion has an oxidation number of 1-, when it combines with Aluminum, Chlorine takes the oxidation number of Aluminum as a subscript, in this case, 3, and the Aluminum takes the oxidation number of Chlorine that is 1(it is implied, that’s why we don’t write it).

  If both elements have the same oxidation numbers, they cancel, you don´t write Fe2S2 for example, those “2” cancel.

numbers with signs are supposed to be superscripts :)

it is easier to learn the names of the anions than the cations because there are a lot of cations, so if we know the oxidation of our anion we can deduce the cation by just seeing the compound, we have FeS, Fe has the oxidation of 2+ and 3+, by knowing that Sulfur as an anion has 2- we deduce that Fe in the compound has the oxidation of 2+ because the sum of both charges must give zero.

there is a little formula to calculate that: 1(x) + 1(2-) = 0 → x -2 = 0 → x = 2 (x is the oxidation number we are trying to determinate).

Stock Nomenclature

• It is the simplest way to write a compound, it is the cation + the oxidation state of the cation in parenthesis with roman numbers + the anion.

• Examples:

  FeS → Iron (II) Sulfide

  Fe2S3 → Iron (III) Sulfide

• If the cation only has 1 oxidation state just write the cation + the anion

• Examples:

  KI → Potassium Iodide

  Li3N → Lithium Nitride

• With polyatomic anions functions the same, cation + the oxidation state of the cation in parenthesis with roman numbers + anion.

• Example:

  CuSO4 → Copper (II) Sulfate

Traditional Nomenclature

• Prefixes will be used based on the amount of oxidation states of the cation, if the cation has only 1 oxidation state, it can be written as stock. If it has **==2 oxidation states use -ous and -ic ==**if it has 3 oxidation states use hypo -ous, -ous, and -ic, if it has 4 oxidation states use hypo -ous, -ous, -ic and per -ic, if it has 5 oxidation states use all of them.

• For example:

  -Ni has 2 oxidation states 2+ and 3+ if we want to write FeO we use Ferrous Oxide because 2+ is the lowest oxidation state.

  -If we were to write Fe2O3 we use Ferric Oxide because 3+ is the highest oxidation state.

• When it comes to acids it means H + as a cation always, in this case, H comes before in symbols and after in naming.

• Example:

  Symbols: H2SO4 → Naming: Sulfuric Acid

• There is only one case with a single anion, we add hydro -ic:

  HCl → Hydrochloric acid

Systematic Nomenclature

• We just look to the subscript in each compound (calculate oxidation number of cation if necessary)

• Examples:

  CO2 → Carbon dioxide

  H2O → Dihydrogen Monoxide

Doesn´t apply with acids