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Chemical Compounds Nomenclature. All things have names, chemical compounds included. But whereas two people can have the same name, no two chemicals can have the same name.

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Chemical Compounds Nomenclature

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Chemical compounds nomenclature

Chemical Compounds Nomenclature

Chemical compounds nomenclature

  • All things have names, chemical compounds included. But whereas two people can have the same name, no two chemicals can have the same name.

  • The system of chemical nomenclature will allow you to give any chemical its proper name and you will also be able to write the correct chemical formula.



  • Most elements do not exist in nature in their pure form, as elements. Gold, Silver, and Platinum are three metals that can be found in the Earth’s crust as elements. They are called precious elements because their occurrence is so rare.

  • There are only 90 naturally occurring elements. Most of these elements are found in nature, only as compounds. Elements combine in may different ways to form the astonishing variety of natural and synthetic compounds that you see and use everyday.

Chemical compounds nomenclature

  • Some elements consist of more than one atom in their natural state. These elements are called diatomic molecules.

    • Hydrogen (H2)

    • Nitrogen (N2)

    • Oxygen (O2)

    • Fluorine (F2)

    • Chlorine (Cl2)

    • Bromine (Br2)

    • Iodine (I2)

    • Astatine (At2)

Chemical and common names

Chemical and Common Names

Chemical compounds nomenclature

  • Because there are so many compounds, chemists have developed a classification system to organize them according to their properties (melting point, boiling point, hardness, conductivity, and solubility).

  • Based on their physical properties, compounds can be classified into two groups: ionic compounds and covalent compounds.

Chemical compounds nomenclature

  • Ionic compounds and covalent compounds display distinct physical properties because of chemical bonding.

  • Bonding involves the interaction between the valence electrons of atoms.

  • Usually a the formation of a bond between atoms creates a compound that is more stable than either of the two atoms on their own.

Naming ions

Naming Ions

  • Naming monoatomic cations

    • To name a monoatomic cation, write the name of the element and add the word “ion” to it.

      • Be2+ is called the Beryllium Ion

  • Naming monoatomic anions

    • To name a monoatomic anion, write the name of the element and change the ending to ide. You can also include the word ion, but it is not necessary.

      • N3- is called Nitride (ion)

  • Transition metals

    Transition Metals

    • All of the transition elements form cations (positive ions).

    • To name a transition metal, write the name of the element then use a Roman numeral to identify the charge. Follow that with the word ion.

      • Fe1+ is the Iron (I) ion

      • Fe2+ is the Iron (II) ion

      • Fe3+ is the Iron (III) ion

    Polyatomic ions

    Polyatomic Ions

    • Polyatomic Ions are tightly bound groups of atoms that behave as a unit.

    • Use the chart provided to name a polyatomic ion.

      • (PO4)3- is the phosphate ion

      • (ClO2)- is the chlorite ion

    Chemical compounds nomenclature

    Compounds can be divided into two basic categories, those which are true binary compounds (contain only two types of elements), and those which contain more than two different types of elements.

    Naming ionic compounds

    Naming Ionic Compounds:

    Monoatomic or simple ions

    Single atoms that have lost or gained one or more electrons

    Form binary ionic compounds (2 simple ions)

    Consist of cations and anions

    Eg. Sodium + chlorine Na+ Cl-

    Chemical compounds nomenclature

    Cations are written first, anions are second (name changes to “-ide” for the anion)

    The total charge must be zero

    Do not write charges in your final answer

    Writing formulas for ionic compounds

    Writing Formulas for Ionic Compounds

    • In binary ionic compounds, the total number of positive charges must equal the total number of negative charges. Basically, the overall charge must be zero.

    • When writing binary ionic formulas, the cation always goes first.

    Chemical compounds nomenclature

    K1+ and Br 1-

    Ca2+ and S2-

    Ca2+ and Cl1-

    Na1+ and P3-

    Fe3+ and O2-

    Form KBr

    Form CaS

    Form CaCl2

    Form Na3P

    Form Fe2O3

    The trick

    The Trick!!

    • Write down the ions

    • Take the charge of the cation (just the number) and write it as the subscript on the anion.

    • Take the charge of the anion (just the number) and write it as the subscript on the cation.

    • This is called the cross over rule!

    • It works for polyatomic ions as well!

    Steps for writing binary ionic formulas when given the name

    Steps for Writing Binary Ionic Formulas When Given the Name

    • Write the symbol for the elements involved with their charges. You can determine the charge based on their position on the periodic table;

      • Group 1 is 1+- Group 5 is 3-

      • Group 2 is 2+- Group 6 is 2-

      • Group 3 is 3+- Group 7 is 1-

      • Group 4 is + or – 4- Group 8 is 0

    • Once you have the symbols with the charges, combine the ions to make the formula.



    • Sodium Oxide

      • Na1+ and O2-

        • Na2O

  • Calcium Phosphide

    • Ca2+ and P3-

      • Ca3P2

  • Iron (III) Sulfide

    • Fe3+ and S2-

    • Fe2S3

  • Calcium Nitrate

    • Ca2+ and NO3-

    • Ca(NO3)2

  • Naming binary ionic compounds

    Naming Binary Ionic Compounds

    • A compound is an inorganic compound that contains two elements.

    • Binary compounds may contain a metal and a non metal. These would be binary ionic compounds.

    • To name a binary ionic compound, name the cation first and then the anion.



    • CaS

      • Calcium ion

      • Sulfide ion

        • Calcium Sulfide

  • BeCl2

    • Beryllium ion

    • Chloride ion

      • Beryllium Chloride

  • Rules for formulas

    Rules for formulas:

    Write the symbols for the ions involved

    eg. Silver and chlorine

    Ag+ and Cl-

    Determine the lowest whole number ratio of ions which will provide an overall net charge of zero

    Ag1+ Cl1- becomes AgCl (silver chloride)

    Example potassium and oxygen

    Example: potassium and oxygen

    potassium - K+

    oxygen -O2-

    K2+ O12-

    becomes K2O potassium oxide

    Naming ionic compounds1

    Naming Ionic Compounds

    Cation is named first

    Anion is named second

    Ending of anion is changed to “ide”



    Multivalent ions

    Multivalent ions

    -certain transition metals can form more than one type of ion, each with a different charge.

    • eg. Cu2+ - copper (II)

      Cu+ - copper (I)

    Multivalent ions continued

    Multivalent ions (continued)

    • The transition metals have various electron configurations that will make them stable

    • Use a roman numeral after the cation to specify its charge (Stock naming system).

    • Eg. Iron (ii) oxideFeO

      Iron (iii) oxideFe2O3

    Stock vs classical

    Stock vs. Classical

    FormulaStock NameClassical Name

    Cu+copper(I) ionCuprous ion

    Cu2+copper(II) ionCupric ion

    Fe2+iron(II) ionFerrous ion

    Fe3+iron(III) ionFerric ion

    Chemical compounds nomenclature

    Fe2+ so this is Iron (II) oxide

    • FeO

      • Iron ion

      • Oxide ion

        • Iron oxide

  • Fe2O3

    • Iron ion

    • Oxide ion

      • Iron oxide

  • No two compounds can have the same name, so the charge on the cation is included in the name as a Roman Numeral.

  • Fe3+ so this is Iron (III) oxide

    Naming of polyatomic compounds

    Naming of Polyatomic Compounds

    • Identify the cation and the anion. (Use the polyatomic chart to identify the polyatomic ion).

    • Mg(NO3)2

      • Magnesium ion

      • Nitrate ion

        • Magnesium Nitrate

    Chemical compounds nomenclature

    • (NH4)2(CO3)

      • Ammonium ion

      • Carbonate ion

        • Ammonium carbonate

  • Fe3(PO4)

    • Iron (I) ion

    • Phosphate ion

      • Iron (I) phosphate

  • Summary of ionic bonding

    Summary of Ionic Bonding…

    • You have learned what happens when the EN difference between atoms is greater than 1.7 – you get an ionic bond.

    • The atom with the higher EN gains the electrons from the atoms with the lower EN, causing the atoms to become charged.

    • Oppositely charged ions attract and that is how the ionic bond is formed.

    Naming molecular compounds

    Naming Molecular Compounds:

    Use prefixes to specify number of atoms of each element in the molecule

    Second element ends with “-ide”

    No charges used in formula

    The prefix “mono-” should not be used on the first element

    • mono

    • di

    • tri

    • tetra

    • penta

    • hexa

    • hepta

    • octa

    • nona

    • deca



    • The prefix “mono” is attached to the name of the second element in the molecule when there is only one atom of that element present.

    • It is not used in the name if the first element if there is only one atom of that element present.



    • N2O5

      • 2 N is dintrogen

      • 5 O is pentaoxide

        • Dinitrogen pentaoxide

  • SF6

    • 1 S is monosulfur, except it is first, so just sulfur

    • 6 F is hexafluoride

      • Sulfur hexafluoride

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