The earlier system of naming chemical compound depending on the source from which it was obtained or on the basis of its structure or properties is known as trivial system. Thus the name urea, from urine, methanol (meaning spirit of wood), citric acid (from citric plant) glucose (sweet), pentane (five), hexane (six) etc., were derived from the Greek words describing their properties and structure. The name based on trivial system is called trivial or common names etc., was based on the source of their occurrence.
Scientist all around the global world uses a standard method for naming chemical compounds. International union of pure and applied chemistry (IUPAC) sponsored to the international committee for set up standards for chemical name.
These standards make easier to use the compounds every day in life. Chemical compound names are very important otherwise the scientists every where used different names for same compound. That will make very dangerous situations in chemical laboratories.
International Union of Pure and Applied Chemistry (IUPAC) Names are used to avoid repeat names of the compound. IUPAC naming are systematic names of organic chemical compounds by international union of pure and applied chemistry. IUPAC names are not always followed in practice, except when it is necessary to give a concise definition to a compound.
International unions of pure and applied chemistry names are very long. International union of pure and applied chemistry method is another method for naming chemical compounds. This IUPAC names are guides detail about what group are attached to that chain and also indicate where they are attached.
IUPAC name for butane is 2-methyl propane. In above shown figure, we can see the three carbon atoms are in a row, which will give the name propane. We have a one carbon that should be attached side of the propane. ‘Meth’ indicates there is one carbon atom in the attached group, so we have to use ‘yl’ in suffix. So the IUPAC name is methyl propane.
Then we should see where a side group attached to the main chain. In this case, the methyl group is attached in the second carbon of the propane. So the full IUPAC name for butane is 2-methyl propane.
Rules for naming compounds are as follows.Binary Ionic Compound (Type I)
This binary atomic compound contain all group I, II, III metal and nonmetal ions. If the compound is binary ion, the following rules should be followed for naming chemical compounds.
- First named the cation (Na+, Al3+), which is positively charged and then named the anion (Cl-, O2-), which is negatively charged.
- A mono atomic (the element which is having only one atom) cation takes its name from the name of the element. For example H+ is called as hydrogen in the names of compounds containing this ion.
- A mono atomic anion takes its name by taking the root of the element name and adding with suffix ‘ide’. For example, H- ion is called as hydride, Cl- ion called as chloride.
Binary Ionic Compound (Type II)
If the compound is under binary ionic compound (type II), the following rules should be followed for naming chemical compounds. This type II contains all transition metal ions with non metal ions.
- First named the cation of a transition metal and then named the anion.
- A mono atomic (the element which is having only one atom) cation takes its name from the name of the element. For example Cu+ is called as copper and Cu2+ is called as copper (II) in the names of compounds containing this ion.
- All the transition metal cation must show its oxidation number after its name with in the parenthesis. For example Iron (II), copper (II), vanadium (V), except Zn2+, Cd2+, and Ag+.
- The cation in group III A – VIA (Sn, Pb, Ga, Bi, etc.,) which is having multiple charges, even though they are not transition metals, oxidation number should named with parenthesis after the name and show its positive charge as a Roman number. For example, Pb2+ is named as Lead (II).
Binary Covalent Compound (Type III)
This binary covalent compound (type III) containing only non metal elements which are not having any charges. These non metal elements are always neutral and also consist of only two elements.
- First named the first element shown in the compound as the element name. For example CO2, first named the first element of the compound as the element name carbon.
- Then named the second element shown in the compound according to anion name, ending in ‘ide’. So the second element of the compound named as oxide.
- Before naming the second element, just see how many atoms of element present in the compound, which is indicated by the subscript of the compound. For example CO2, in these 2 atoms of oxide present in the compound, so it has the ‘di’ in prefix of second compound name, so the name of the compound is carbon dioxide.
- If the first element present in more than once, assumed it is present only once, hence just the name of the element. However, if the first element present more than once, then you should specify the number of times it is duplicated like di, tri, tetra, etc. Ex: P2O5 – diphosphorous pentoxide
Common Acid and Anion Names
If the compound is common acid and anion, the following rules should be followed.
1. If the acids are hydro acid, which do not contain oxygen should be named first as hydro then halogen name with ‘ic’ in suffix.
HCl – Hydro chloric acid
H2S – Hydro sulphuric acid
HF – Hydro fluoric acid
2. If the acids are oxo acids, first recognize as polyatomic ions with hydrogen at the beginning of the formula. Then name with ‘ous’ and ‘ic’ in suffix. If acid with more than one oxygen atoms use ‘ic’ in suffix.
HNO3 – Nitric acid
HNO2 – nitrous acid
3. Compound containing polyatomic anions are named using Type I or Type II naming system. For example, sodium salt of nitric acid is named as sodium nitrate – NaNO3.If the compound contains two non-metals in a covalent bond, the following rules should be followed.
- First name the least electronegative element.
- If the compound contains hydrogen, first name of the compound is hydrogen,
- Then the compound number of atoms of each element present in the compound is indicated by prefix.
- If first element has only one atom, we should not use any prefix for that element.
Naming chemical compounds are very important to identify the chemical compounds. Before naming the compound we should know the names and symbols for all elements like group I, and group II, halogen group, noble gases and some metals which are used frequently also we have to found what kind of compound it is.
- Chemical compounds are mainly divided in to two major types, such as ionic compound which contain metal and nonmetal, and covalent compound which contain only non metals.
- Ionic compounds are formed when metal give up its electrons to non metal. These ionic compounds can be easily recognized and naming them also very easy.
- Ionic compounds can further subdivided in to ionic compound without transition metal and ionic compound with transition metal.
- For naming ionic compounds without transition metal, first name the first element of the metal compound, simply name the metal name of the first element. Then name the second element of the non metal compound.
- The name of the non metal element should ending with suffix ‘ide’. For example consider Al2O3, the subscript of the compound indicates that how many atoms of elements present in that compound.
- These subscripts do not affect the name of the compound. So the first element name of the compound is named as aluminum.
Then name the second element of the compound is oxide, we drop the ending on oxygen and add ‘ide’.
AlCl3 – Aluminum chloride
Na2S - Sodium sulfide
K2O - Potassium oxide
For naming ionic compound with transition metal is some what difficult then ionic compound without transition metal, since the transition metal can form more than one compound. A transition metal is an element with an atomic number of 21-30, 39-48, and 51-80 from the pediatric table. The transition metal in d and f blocks has more than one charge.
For example, the combination of iron and chlorine can form two different compounds, like FeCl2 and FeCl3. In such case we use Roman numeral to indicate the charge on the metal ions. For naming of ionic compound with a transition metal, specify the charge of the transition metal ions with Roman numeral.Example :
Fe (Cl2) – Iron (II) chloride
Fe (Cl3) – Iron (III) chloride
The ions which are having two or more nonmetal atoms are called as polyatomic ions and they are covalently bonded together. Some of the polyatomic ion as follows.
The entire group of polyatomic ions has a positive or negative charge. Polyatomic ions are commonly forming two or more covalent compounds. The covalent compounds are formed from non-metals that share electrons. For example carbon and oxygen can form both carbon monoxide as well as carbon dioxide we cannot call both the compound as carbon oxide. To distinguish this covalent compound prefixes are used, these prefixes indicate how many atoms of each element are present in the compound.Example :
– Carbon dioxide
– Dinitrogen trisulfide