1. 5.7 NAMES & FORMULAS OF IONIC COMPOUNDS

2. The International Union of Pure & Applied Chemistry (IUPAC)
Decides on a common naming system known by scientists across the world
Recall—Ionic Compounds:2 elements; a metal & a non-metal
Therefore their names have 2 parts
first part metal ion
second part non-metal ion
The first part of the name is the same as the name of the neutral metal atom
The second part of the name changes the non-metal ending to “ide”

3. Examples magnesium + chlorine = magnesium chloride
(metal) (non-metal) (ionic compound)
aluminum + oxygen = aluminum oxide
(metal) (non-metal) (ionic compound)

4. Writing these chemical formulas.
Remember… electrons move from metal atoms to non-metal atoms
The charged ions attract other ions of the opposite charge until the charges balance out (positive + negative = zero)
The compound that forms is electrically neutral
*** # of positive charges = # of negative charges***

5. Chemical Formula of Magnesium Chloride
1 Write the symbols of the elements, with the metal on the left and the non-metal on the right
Mg Cl
2 Add the ionic charge of each ion above the symbol
3 Determine how many ions of each are required to bring the total charge to zero.
1 (+2) (-1) = 0
Mg Cl

6. Magnesium Chloride Continued…
4 Write the chemical formula using the coefficients in front of each as the subscripts
MgCl2 magnesium chloride
***Do not write the subscript “1” in chemical formulas because the symbol itself represents one ion ***

7. CRISS CROSS RULE (An easier way to write chemical formulas)
Ex: Magnesium Chloride
1 Write the symbols for each element Mg Cl
2 Write the ionic charge above each symbol
(the # e- gained/lost to become an ion)
3 Drop the +/- sign
4 Criss cross the numbers of the ionic charges
5 Write the numbers as subscripts : MgCl2
6 Do not write a 1 as a subscript as the 1 is already assumed

8. Sometimes………
Occasionally you get an answer with two identical subscripts
Ex: Al3N3
Write the compound with subscripts in lowest terms
Ex: AlN

9. This is what it all means!
MgCl2
There is one atom of magnesium in the molecule
There are two atoms of chlorine in the molecule
Magnesium has two electrons to give away. Chlorine only needs 1 electron. There fore two chlorines are needed to take the two available electrons from magnesium.

10. Elements with Multiple Charges
Some elements have two stable cations.
e.g. Fe2+ and Fe3+
Fe2+ is called Iron (II) and Fe3+ is called Iron (III)
There are two different compounds of iron and chlorine
FeCl2 (light green solid) and FeCl3 ( yellow-brown solid)
Named the same way, except insert rounded brackets with Roman numerals indicating the ionic charge

11. Some other Elements with Multiple Ionic Charges
Metal
Chemical symbol of element
Chemical Symbols of ions
Names of Ions
copper Cu
Cu+
Cu2+
copper (I)
copper (II)
Iron Fe
Fe2+
Fe3+
Iron (II)
Iron(III)
Lead PB
Pb2+
Pb4+
lead (II)
lead (IV)
Manganese Mn
Mn2+
Mn4+
manganese (II)
Manganese (IV)
tin Sn
Sn2+
Sn4+
tin(II)
tin(IV)

12. Naming these Compounds
Whenever you name a compound containing a metal, ALWAYS check to see if the metal has more than one ionic charge.
metal ( Roman Numeral ) Non metal (with “ide”)
If it does, use reverse criss cross to determine the correct “bracket”
FeCl3
Double check that the non metal has the correct ionic charge as well
If so then it is Fe3+ and the compounds name is iron (III) chloride

13. FeP Another Example FeP
FeP
But iron’s valence is 2 or 3 and phosphorous’ valence is 3,5 or 4. Therefore the common valence is 3.
Iron (III) Phosphide

14. Homework
Two Handouts
Textbook: pg 200 # 2-5, 7, 9