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Naming and Writing Formulas   Tags: chemical formulas, naming formulas, turley, writing formulas  

This page gives information on naming and writing of chemical formulas.
Last Updated: Dec 9, 2011 URL: Print Guide RSS Updates
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Keri Turley
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Oxidation Number Rules

These rules are used for Ionic Compounds: (metal + non-metal)

1. Cations (positive ions) are always written first

2. Free elements = 0

   elements by themselves, ex. Zn, Ag, Na

   also includes diatomic molecules:

   Hydrogen, Nitrogen, Fluorine, Oxygen, Iodine, Chlorine and Bromine

3. Ion charge = oxidation number

4. Hydrogen usually is +1

5. Oxygen usually is -2

6. Family IA = +1

   Family IIA = +2

7. Sum of compound = 0

    Sum of ion = charge on ion


Covalent Bonding Prefixes

Prefixes are ONLY used for covalent compounds.

Mono-    1
Di- 2
Tri- 3
Tetra- 4
Penta- 5
Hexa- 6
Hepta- 7
Octa- 8
Nona- 9
Deca- 10




Click here for a refresher on electronegativity.

Electronegativity differences:

0-0.4 = nonpolar covalent

>0.4-1.7 = polar covalent

>1.7 = ionic bonds

Click here for an electronegativity value chart.  The large numbers are the electronegativity numbers.


Ionic vs. Covalent

When you name a formula you need to decide if the compound is ionic or covalently bonded.

Click here to see the notes on ionic bonding

Click here to see notes on covalent bonding.  Click through all the pages to see the differences between ionic and covalent bonding.  Or use this one, go to this link and go down to Chapter 8 Covalent Bonding and open the ppt or pdf file.   Click here.

Click here to see notes on naming two (binary) element covalent compounds.


Naming Compounds

Go to these sites to practice naming compounds.  Make sure you read the notes first then go to the practice links.  Be careful that you understand the different between ionic and covalent bonding so you know when to use each type of naming.

Ionic Naming Notes

Ionic Naming Practice

Ionic Naming Practice II

Covalent Naming Notes

Covalent Naming Practice


Video on Bonding

Watch this video to get extra explanation on bonding.


Naming and Writing Chemical Formulas

View this podcast to get more explanation on how to write and name chemical formulas.  Please note;  he makes one mistake by writing Tin as Tn instead of Sn, otherwise all the information is good.



Search for Bonding


Search for Bonding


ionic Bonds

An example of an ionic bond.

Source for image click here

In this example the one atom donates an electron to the other atom.  In the second set of pictures the elements are no longer atoms, but are ions (charged particles) because one element has 1 electron less and the other atom has 1 electron more.


Source for image click here   


Covalent Bonds

An example of a covalent bond.  notice the hydrogens are sharing electrons with the carbon.

Covalent bond

Source for image click here   


Links to Periodic Tables

Click here to link to a basic perdioc table

Click here to link to a dynamic periodic table

Click here to link to a Periodic Table with oxidation states

Click here to link to a site to choose which version of periodic table you want to print


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