Writing and Naming Ionic and Covalent Compounds

What are Ionic Compounds?

Well, basically they are compounds where two or more ions are held together by electric attraction.
One of the ions are positively charged, and the other is negatively charged. When writing the compounds, always remember that the positively charged ion (metal) is always first! 

To make life easier, looking at the periodic table, the positively charged ions (metals) are on the left side and the negatively charged ions (non-metals) are on the right side.

Writing and Naming Ionic Compounds

The Cross over rule:

1)Write the symbols
2)Write the charges
3)Cross over the charges from top to bottom
4)Remove the chages

In example 1 we took their charges and "cross-over" from top to bottom. Remember, before writing the formula down make sure that charges are correct and the metal is written first. The reason we do this is because we want the resulting charge to equal zero!

Ex 2.  You will find yourself coming across an element that has 2 charges instead of 1, but dont panic! turn that frown upside down, it only takes one more easy step :)
For instance, take copper (Cu), it has a charge of +2 and +1. Just follow the same steps as example 1, but make sure you use roman numerals to tell us which charge you are using.

a) Copper (I) oxide    =      Cu2O

b) SnCl4    =    Tin (IV) Cloride


Also, under Ionic compounds are Complex ions: A group of atoms that behave as one atom.
You can find these ions behind the periodic table Ms. Chen distributed :)

*Writing these formulas only requires the same steps as the one given before.The underlined elements are complex ions and are found in the back of the periodic table or the picture shown above.

a) Calcium Hydroxide  =  Ca(OH)2    < when dealing with complex ions, put brackets to show the 2  goes into both O and H

b) Copper (II) Nitrite   =  Cu(NO2)2

What are Covalent Compounds?

It is a compound in which two atoms bond, they share electrons rather than transfer. Covalent compounds are formed when two non-metals bond to each other whereas ionic compounds form when metals bond to non-metals.
Diatomic Elements is another thing you got to watch out for in covalent compounds. They are a special group of molecules that consist of 2 identical atoms, which are:
                                                H2, O2, F2, Br2, I2, N2, Cl2



In covalent compounds we use greek prefixes to indicate the number of atoms
*memorize this for tests in the furture*
Mono - 1                           Penta - 5                        Octa - 8     
Di - 2                                 Hexa - 6                        Nona - 9      
Tri - 3                                Hepta - 7                       Deca - 10
Tera - 4

Writing and Naming Ionic Compounds: 

*The cross over process is not needed for writing ionic formulas

Ex  a) CO2     =     Carbon dioxide

      b) N2O4     =    Dinitrogen tetroxide

      c) Sulphur trioxide      =      SO3


VIDEOS! For all you visual learners, like me :)

Ionic Compounds:  http://www.youtube.com/watch?v=vscoYh6m46M
Covalent Compounds: http://www.youtube.com/watch?v=fxE1KOeNZXw

Enjoy :)