Wednesday- June 2, 1999- Ions, Lewis Dot Structures, and Nomenclature
Ion - any element which loses OR gains an electron.
    WHY? - The noble gases have stable octets(8). ALL the elements on the periodic table want to be like a noble gas and have 8 electrons in their outside shell. The only way they can achieve this is to hook up with other elements.

Example:
Chlorine-( 17 electrons) -     [Ne]3s23p5    - 7 electrons in the outside shell
What does chlorine want? It needs to gain 1 electron to be like a noble gas.
If chlorine gains an electron, it will have 17 protons in the nucleus and 18 electrons outside.
+17 + (-18) = -1      Therefore the charge of a chlorine ion is  -1 or written as   Cl-1
 

Sodium- (11 electrons) - [Ne] 3s1 - 1 electron in the outside shell
In this case, it would be a whole lot easier for sodium to LOSE 1 electron to be like a noble gas rather than gain 7. If sodium loses an electron, it will have 11 protons in the nucleus and 10 electrons outside.
+11 + (-10) = +1     Therefore the charge of a sodium ion is +1 or written as  Na+1

Compound- A substance created when 2 or more ions are combined. The substance can have entirely new properties than the original elements used to make it.
    Rules:
                1)When making compound the NET CHARGE must equal zero
                2)Always write the positive ion(CATION) first.
                3)Always write the negative ion(ANION) second.

Example:     Na+1   +     Cl-1  =   NaCl       If the #s are the same they will cancel out.


Magnesium ( 12 electrons) - [Ne]3s2- Magnesium Loses 2 electrons -  Mg+2
Bromine( 35 electrons)  - [Ar] 4s23d104p5 = Bromine gains 1 electron - Br-1

To make the compound,     Mg+2 +  Br-1  =  but wait!!...... it appears that you need 2 bromines at -1 each so that the NET CHARGE equals ZERO.
 Mg+2 +  Br-1 + Br-1   =   MgBr2
When you write HOW MANY of an element you need, you use a subscript.


Aluminum -( 13 electrons) - [Ne]3s23p1 - Aluminum loses 3 e-      Al+3
Sulfur -( 16 electrons)   - [Ne]3s23p4 - Sulfur gains 2e-                   S-2

This example takes some thought. It appear that we will need 2 aluminums and 3 sulfurs
Al+3 +   Al+3   +   S-2   +   S-2   +  S-2      +6 + (-6) = 0

Al2S3


The shortcut!
You can now simply cross your charges........BUT DO NOT BRING DOWN THE SIGN!

 
= MgBr2     You don't need to bring down a 1



 
= Al2S3    Notice we are not bringing down the sign only the #.

 


You can also take a compound and use the shortcut to figure out the charges of each ion. In other words, use it BACKWARDS!
= Fe +3     and   O-2
Why is this useful?  One way is figuring out the charge of a transition metal.
Iron is in the "d" sub level. We don't know exactly what it's charge is unless we are told. The written formula however tell us it is IRON III. It could also be IRON II.

Transition metal - As it's name implies, any metal that can have multiple charges. A roman numeral is used when writing the name.

Lewis-Dot Structures
A visual representation of how the electrons are lost and gained.(They are actually shared most of the time)

Example
Hydrogen ( 1 electron) - 1s1   H+1         Carbon (6 electron) - [He]2s22p2     C-4
To make the compound we need 4 hydrogens and 1 carbon.

What you will do is show 4 hydrogens each will 1 electron around it.
Then you will show 1 carbon with 4 electrons around it.
Since carbon needs 4 electrons to form a stable octet, you will show the 4 hydrogens giving the carbon the electrons it needs. You will then show the complete compound with carbon having 8 electron around it.
            


Calcium ( 20 electrons) - [Ne]4s2 - Ca+2   (loses 2 electrons)
Chlorine (17 electrons) - [Ne]3s23p5 - Cl-1 ( gains 1)

It appears that we need 1 calcium and 2 chlorines. ( Remember, we want a NET CHARGE of ZERO)  Ca+2 + Cl-1 + Cl-1 ---- CaCl2
                   

Each chlorine has 8 electrons around it and are therefore stable.


The Nomenclature(Naming compounds) notes will be provided using a special worksheet.