Chemical nomenclature

Welcome to my “Entertaining Chemistry” blog. My name is Aiym Bigazy. I am a chemistry major student at Nazarbayev University. I am interested in chemistry, because chemistry is a central science; hence other sciences, particularly physics and biology, are tightly connected with it. Moreover, chemistry is indefeasible part of our lives, as every object surrounding us has a chemical nature. In this blog I would like to introduce chemical nomenclature, which is used for naming compounds.

First of all, chemical nomenclature is a set of rules to name the compounds established by IUPAC. IUPAC abbreviates as International Union of Pure and Applied Chemistry. These rules were designed because of difficulties in naming of infinite number of compounds. These include, organic and inorganic substances, which can be composed of various elements with different properties, for example, metals and nonmetals, different oxidation states, etc. 

Figure 1. Periodic table of chemical compounds.
Source

Let’s begin with the brief explanation of elements in Periodic Table. Vertical columns marked as IA-VIIIA are called groups. The elements of first group are called alkaline metals and they consist of lithium, sodium, potassium, etc. The second group elements are called alkaline-earth metals, these are beryllium, magnesium and others. Groups IIIB- VIIIB (red colored) are transition metals, which have several oxidation states (charges). Beginning from IVA to VIA are nonmetals; and Fluoride, Chloride, Bromide, Iodide, Astatine are called halogens. The last group elements are the least reactive and called Nobel gases. Names and symbols of all elements you can see here.

According to Zumdahl and DeCoste, there are following rules in naming compounds:

1)  In binary ionic compounds (consist of positive and negative ions), firstly, cation (positive) is named, secondly, anion (negative) is named. Cations are usually metals, anions are nonmentals.

                                    Metal + Nonmetal + ide suffix

If metal  forms more than one cation (with different oxidation states), then Roman numeral showing the oxidation state of cation is added. For example, NaCl is called sodium chloride, because sodium has charge +1 only, whereas CuCl₂ is called copper (II) chloride, because copper can have charge +1 and +2, in this case it is +2.

Metal + Roman numeral + Nonmetal + ide suffix

    2)  If a compound contains more than two elements it is called polyatomic, they are named in the same manner, but names of polyatomic ions are also established by IUPAC and should be memorized. For example, Na₂SO₄ is sodium sulfate, Mg(OH)₂ is magnesium hydroxide; here is the list of polyatomic ions. 

     

      3)  Binary covalent compounds consist of two nonmetals, but their names are similar with ionic compounds. However, there are some rules that should be applied to naming covalent compounds:

•        Firstly, the element at the beginning of the formula is named (cation)
•       Secondly, negative ion is named, which is the second element
•       When a compound contains two nonmetals or more, to determine the number of atoms of each element prefixes are used:

  

  Figure 2. Prefixes determining the numbers.
  Source

For example, P₂O₅  is called diphosphorus pentoxide, and N₂O₄ is dinitrogen tetroxide.

Moreover, there is more complicated system of naming organic compounds and due to the word limit it will not be covered in this blog.

Summary:

 

Figure 3. Naming chemical compounds.
Source

References

"Formula, Name." http://www.ars-   chemia.net/Classes/68/Notes/List_of_polyatomic_ions.pdf. http://www.ars-chemia.net/Classes/68/Notes/List_of_polyatomic_ions.pdf (accessed September 30, 2014).

"Welcome to the International Union of Pure and Applied Chemistry." IUPAC.   http://www.iupac.org/ (accessed September 30, 2014).

Zumdahl, Steven S., and Donald J. DeCoste. Chemical principles. Seventh ed. Brooks: Cengage Learning, 2013.