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So Far We’ve Learned:
That atoms are made up of Protons, Neutrons, and Electrons
The identity of an atom is determined by the number of protons in the nucleus
BUT, compounds form due to the interactions between electrons
How are Electrons Involved?
•I. Either Shared (Covalent) or Transferred (Ionic)
Using the Periodic Table, we can predict an element’s electron behavior.
A (-) charge = gained electrons
A (+) charge = lost electrons
General Rules (ionic):
Metals will ALWAYS form + ions (cations)
Non-metals will ALWAYS form – ions (anions)
Chemical compounds form from the interaction between oppositely charged ions:
• Na+1 + Cl-1 -------> NaCl
• sodium ion + chloride ion ----> sodium chloride
BIG IDEA:
Every element is trying to rearrange its electrons (by gaining or losing them) in order to “look like” a noble gas element.
This is called achieving a “Noble Gas Configuration. (Full outer electron shell)
Identifying IonsName Common Ion (Na+1) Cation or Anion Anion “ide” name
Strontium
Iodine
Nitrogen
Oxygen
Lithium
Magnesium
Silver
Zinc
Iron (II)
Phosphorous
Sulfur
Aluminum
Fluorine
Chlorine
Potassium
Bromine
Cesium
Francium
Chromium (VI)
When Ions Combine, the Compound MUST
be NeutralAll (+) charges must be cancelled by (-) charges
Need to combine ions in smallest proportion that will cancel charges.
ANSWERS:LiCl (Li+1 + Cl-1)
MgCl2 (Mg+2 + 2Cl-1)
AlCl3 (Al+3 + 3Cl-1)
Li2O (2Li+1 + O-2)
MgO (Mg+2 + O-2)
H2S (2H+1 + S-2)
Anatomy of a Chemical Formula
1.Symbols for the elements in the compound
2.Numbers called subscripts that indicate how many atoms of an element are present:
• AlCl3 = 1 Al and 3 Cl
• This should makes sense because Al has a +3 charge and Cl has a -1 charge
3.The subscript is ONLY associated with the element symbol to the immediate left.
Polyatomic Ions
“Poly-” means many
Polyatomic ions are charged particles that consist of more than one atom
These ions can combine just like ions formed from single elements
Just One Catch!
If more than one polyatomic ion is needed, the formula for the compound will need to have parenthesis around this ion
Example: Mg+2 + PO4-3 ----> Mg3(PO4)2
Polyatomic Ions May be Used Like Other
IonsJust like Sodium (Na+) can combine with chloride (Cl-1), to make NaCl
A polyatomic ion called ammonium (NH4
+1) can combine with chloride (Cl-1) to make NH4Cl
The N and 4 H’s that make up NH4 , collectively loose 1 electron to become NH4
+1
Goal: Make Compounds Using Paper Models of
Ions
KBr Postassium Bromide
K3PO4 Potassium Phosphate
Goal for today: Complete as much of chartas possible. Do NOT Name compounds.
Naming Ionic Compounds
1.Determine the ions that make up the compound. (Use Periodic Table or “Common Ions Chart”)
2.Write the name of the POSITIVE ion first
3.Write the name of the NEGATIVE ion second. (Sometimes the name of this ion will change slightly)
Negative Ion Names
Name endingchanges to
“-ide”
Non-metal elements in columns 14-17 will form negative ions with names ending in “-
ide”.
Examples:
•Chlorine becomes chloride
•Fluorine becomes fluoride
•Oxygen becomes oxide
•Phosphorous becomes phosphide
•Nitrogen becomes nitride
If polyatomic ions are used...
Naming is easy!
Just put the names of the ions together (positive first, negative second)
No Name changes are needed
• Example:
• Mg3(PO4)2 is named Magnesium phosphate
Positive ion Negative ion