Definition of Inorganic Compounds

In this work we will focus on the formulation and nomenclature of inorganic compounds, from the simplest to the you go out. We will work with basic oxides, acid oxides, hydroxides, oxoacids, non-metal hydrides and metal hydrides. Finally, we will come to the formulation of oxosalts and hydrosalts.

If we think about it from the point of view of a network, we can say that everything starts with molecular oxygen. If it is combined with metals or non-metals, the paths fork. If combined with metals, basic oxides are formed. Then if this basic oxide is combined with Water, hydroxides are formed.

On the other hand, if diatomic oxygen is combined with non-metals, acid oxides are formed. Then, if the acidic oxide is combined with water, acids (oxoacids) are formed.

Another path opens up when we combine hydrogen with metals or non-metals. When combined with nonmetals, nonmetallic hydrides (hydracids) are formed, while when combined with a metal a metal hydride is formed.

Finally, the combination of some of these compounds results in the formation of salts. When a hydroxide is combined with an oxo acid, an oxosal (plus water) is formed. Whereas, when we combine a hydroxide with a hydracid, a hydrosalt (more water) is formed.

To understand how to formulate compounds there are some basic issues that we must know. First, the oxidation number of an element or substance simple is zero and, on the other hand, if the compound formed is neutral (no charge), the sum of the oxidation numbers multiplied by the atomicity of the element must be zero.

If you have a charged species, then its oxidation number is equal to the charge of that ion, while if the compound is charged, the sum of the oxidation numbers multiplied by the atomicity of the element must equal the charge of ion.

Also, some other basic rules are the oxidation states of hydrogen and oxygen. In general, the oxidation state of oxygen is -2 (except in peroxides, which is -1). In contrast, hydrogen has oxidation number +1 (with exception when combined with metals, it acts with oxidation state -1).

On the other hand, keep in mind that in general, metals form cations by giving up electrons and resembling their electronic configuration to that of the closest noble gas.

In the following examples we will seek to interpret the oxidation states and atomicities of the following compounds, a step that is key to be able to formulate the different chemical compounds:

Suppose the following compound:

\({{H}_{2}}S{{O}_{4}}\)

Earlier we mentioned that hydrogen, in general, has oxidation state +1 while oxygen -2. So, the algebraic sum reduces to:

\(2~x~\left( +1 \right)+State~of~oxidation~of~sulfur+4~x~\left( -2 \right)=0\)

Since it is a neutral compound, the sum must equal zero (it has no charge). Now, we multiply each oxidation state by the number of atoms of that element present in the compound (its atomicity). So, by clearing this equation, where the only unknown is the oxidation state of sulfur, we see that this results in (+6). When checking, it is valid, since sulfur can have this oxidation state.

We see another example, the case of a salt:

\(Au{{\left(ClO \right)}_{3}}\)

On this occasion, we see a group (\(ClO\)) that appears three times, so the oxidation state of gold will be conditioned by this group exhibit. Gold has two possible oxidation states (+1) and (+3). Since it is a neutral salt, the sum of the charges must be 0. If gold had oxidation state +1, the three groups of the chlorate anion would have to add (among the three) charge (-1), which is impossible. As there are three chlorate groups, it is understood that the charge of gold is (+3) while each chlorate group has a negative charge, being: ClO^-. Now, oxygen has an oxidation state of (-2), so for the charge of the resulting ion to be (-1), the oxidation number of chlorine must necessarily be +1.

Nomenclature of inorganic compounds

When naming the simplest and most inorganic chemical compounds, three types of universally known nomenclatures are defined. The first one is based on its atomicity, the second one is known by the name of its creator Numera de Stock, and the third and last one is the traditional one.

If we name compounds by their atomicity, we must know the Greek prefixes (mono-, di-, tri-, tetra-, among others). Instead, if we use the Numeral Stock nomenclature, the compound is named and if the metallic element has more than one state of possible oxidation of the oxidation number with which it intervenes in the compound. Lastly, the traditional nomenclature adds prefixes and suffixes according to the oxidation state. In the event that there is only one possible state of aggregation, no suffixes are added, while if there are two or more, the following is defined:

Two oxidation states - the following suffixes are added: to the minor “-oso” and to the major “-ico”

Three oxidation states – the following prefixes and suffixes are added: to the minor “hypo-” and “-oso”, to the intermediate “-oso” and to the major “-ico”.

Four oxidation states – the following prefixes and suffixes are added: to the minor “hypo-” and “-oso”, to the intermediate “-oso”, to the following “-ico” and to the major “per-” and “-ico” .

Now we will see each particular compound and its nomenclature.

basic oxides

We'll start with the basic oxides, combining a metal with molecular oxygen:

\(4~Au+~3~{{O}_{2}}\to 2~A{{u}_{2}}{{O}_{3}}\)

In this case, gold has two possible oxidation states (+1) and (+3) and you are using the higher one. So the nomenclature boils down to:

Atomic nomenclature: diorus trioxide.
Stock nomenclature: gold(III) oxide.
Traditional nomenclature: auric oxide.

acid oxides

In this case we combine a non-metal with molecular oxygen:

\(2~C{{l}_{2}}+~5~{{O}_{2}}\to 2~C{{l}_{2}}{{O}_{5}} \)

In this case, chlorine has four possible oxidation states and is using the major intermediate. So the nomenclature boils down to:

Atomicity nomenclature: dichloro pentoxide.
Stock nomenclature: Chlorine (V) oxide.
Traditional nomenclature: chloric oxide.

Hydroxides

They are formed by combining a basic oxide with water, therefore:

\(N{{a}_{2}}O+~{{H}_{2}}O~\to 2~NaOH\)

In this case, the nomenclature is defined, in general, with the traditional nomenclature: sodium hydroxide.

oxoacids

They are composed by combining an acid oxide with water, for example the following case:

\({{N}_{2}}{{O}_{5}}+~{{H}_{2}}O~\to 2~HN{{O}_{3}}\)

To define its name, we need to understand what oxidation state the central nitrogen atom has. In this case, we can take it from its oxide, where we see that the oxidation state is 5, the highest possible. It should be noted that Stock indicates the presence of the group formed by the non-metal and the oxygen with the suffix “-ato”. Thus:

Nomenclature by atomicity: hydrogen trioxonitrate.

Stock nomenclature: hydrogen nitrate (V).
Traditional nomenclature: nitric acid.
metal hydrides

When combining diatomic hydrogen with a metal, a hydride is formed, remembering that here the oxidation state of hydrogen is (-1). For example:

\(2~Li+{{H}_{2}}~\to 2~LiH\)

Atomic nomenclature: lithium monohydride
Stock nomenclature: lithium (I) hydride.
Traditional nomenclature: lithium hydride

non-metal hydrides

Also known as hydracids when dissolved in water, they arise from the combination of diatomic hydrogen with a nonmetal. Such is the case of:

\(2~Br+{{H}_{2}}~\to 2~HBr\)

If it is in the gaseous state, the suffix “-ide” is added: hydrogen bromide.

In the case of being in solution, is called hydrobromic acid. That is, it should be mentioned as an acid, coming from a hydride with the suffix "-hydric".

You go out

The salts formed by a metal and a non-metal, the nomenclature mentioned above is preserved. Example:

\(FeC{{l}_{3}}\)

Atomic nomenclature: iron trichloride.
Stock nomenclature: iron (III) chloride.
Traditional nomenclature: ferric chloride.

Those neutral salts, oxosalts or oxysalts, which arise from the combination of a hydroxide with an oxoacid, are named as follows:

\(HN{{O}_{3}}+KOH~\to KN{{O}_{3}}+~{{H}_{2}}O~\)

In this case, the traditional nomenclature is the most used and its name would be: potassium nitrate or potassium nitrate, since the metal has only one possible state of oxidation.