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Chemical Nomenclature

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The activities and of the technical arts practiced prior to the founding of what we now know as the science of chemistry produced a rich vocabulary for describing chemical substances although the names for individual species gave little indication of composition. However almost as soon as the true science of chemistry was established a system of chemical nomenclature was developed by Guyton de Morveau in 1782.

The new chemical nomenclature introduced by Guyton de Morveau, Lavoisier, Berthollet and Foursroy in their Method of chemical Nomenclature of 1787, instead that the names of compounds should represent the constitutive elements and their relative proportions. A system of rules used to assign a name of particular substance called chemical nomenclature.

Chemical Nomenclature Rules

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IUPAC has a set of rules that all scientists try to follow when naming compounds. Known as the rules of chemical nomenclature, they establish patterns to follow in naming existing compounds as well as compounds that have yet to be determined.

The name of the compound mentions the elements in the order given in the formula. These rules apply to binary molecular compounds-those containing two elements that are both non metals.
  1. Name the first element using the exact element name.
  2. Name the second element by writing the stem name of the element with the suffix -ide.
  3. Add prefixes to each element name to denote the subscript of the element in the formula. Generally the prefix mono is used only on the second element in the binary compound to distinguish from other examples containing multiple atoms.


In the development of nomenclature several systems have emerged for the construction of chemical names, each system has its own inherent logic and set of rules.

Number Names
1 mono
2
di
3
tri
4
tetra
5
penta
6
hexa
7
hepta
8
octa
9
nona
10
deca

Chemical Nomenclature Chart

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The word nomenclature simply means naming. Chemical naming falls into two main groups: that for ionic compounds formed of positive and negative ions, and that for non ionic compounds. There are many times when having names for chemicals is more convenient than having their formulas.

For ionic compounds the nomenclature(naming) involves three kinds.
  1. Binary compounds
  2. Compounds of polyatomic ions (ions with more than one atoms)
  3. Compounds of multivalent ions (ions with more than one charge)


The naming strategy for binary compounds is to write the name of the first element, add part of the name of the second element and end with -ide. The part of the name of the second element used is best illustrated by examples.

S.No
Ions
Name
1
H+ Hydrogen
2
Li+ Lithium
3
Na+
Sodium
4
K+
Potassium
5
Mg2+
Magnesium
6
Ca2+
Calcium
7
Ba2+
Barium
8Al3+
Aluminum
9
Ag+
Silver


For some simple negative ions the chart is given below.

S.No
Ions
Name
1 H-
Hydride
2
F-
Fluoride
3
Cl-
Chloride
4
Br-
Bromide
5I-
Iodide
6
O2-
Oxide
7
S2-
Sulfide
8
N3-
Nitride

Chemistry nomenclature made easy by writing formulas and names for chemical compounds. Remember to insert subscripts to make the positive charges equal the negative charges.

S.No Elements involved Ions
Formulas
Names
1
Sodium and fluorine Na+, F- NaF Sodium Fluoride
2
Aluminum and chlorine Al3+, Cl-
AlCl3 Aluminum chloride
3
Potassium and oxygen
K+, O2- K2O Potassium oxide
4
Calcium and sulfur
Ca2+, S2- CaS Calcium sulfide

Chemical Nomenclature Flowchart

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Different rules apply for naming various types of binary compounds. Consider three types of compounds and naming each requires different procedures.
  1. Type 1 - Ionic compounds with metals that always form a cation with the same charge.
  2. Type 2 - Ionic compounds with metals (usually transition metals) that form cations with various charges.
  3. Type 3 - Compounds that contain only non metals.

The flow chart given will help to name the binary compounds of various types.

Chemical Nomenclature Chart

Formulas and Nomenclature Chemistry Problems

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Chemical nomenclature is the organized system for naming of substance. A unique name describes each compound. Chemical nomenclature practice use names and formulas to identify the compounds.

Solved Examples

Question 1: Name the compounds
  1. BaI2
  2. MgO

Solution:
 
To write the name of these compounds
  1. First write the name of the cation followed by the name of the anion.
  2. Second is the anion is generally a non metal and add suffix -ide .

So the name of the compound
  1. BaI2 $\rightarrow$ Barium iodide
  2. MgO $\rightarrow$ Magnesium oxide

 

Question 2: Write the formulas of the compounds.
  1. Sodium sulfide
  2. Potassium fluoride
  3. Calcium chloride

Solution:
 
The strategy is to balance the charges to zero with appropriate subscript. Subscripts of cation and anion are adjusted so that the compound overall will be neutral.
  1. Sodium sulfide $\rightarrow$ Na2S
  2. Potassium fluoride $\rightarrow$ KF
  3. Calcium chloride $\rightarrow$ CaCl2