Transcript Writing Formulas and Naming Compounds

WRITING FORMULAS AND NAMING
COMPOUNDS
Review
What information is in a chemical formula?
What chemical formulas do you already know?
Do they represent ionic or covalent
compounds?
Oxidation Numbers -Patterns
Remember the periodic tables you created,
what was the same for all of the elements in
group 1 (H, Li, Na, K, Rb, Cs, Fr)? Group 2?
Groups 13-18? Why does group 18 rarely, if
ever, form bonds with other elements?\
What does this information tell you about the
resulting charges of ions that form?
http://www.elementsdatabase.com/
Group 1 - 1+
Group 2 - 2+
Group 13 – 3+
Group 14 – 4+
Group 15 – 3Group 16 – 2Group 17 – 1Group 18 – Complete shell, very stable
Binary Ionic Compounds
Binary compound is a compound made of two
elements.
Review - What is the charge on an ionic
compound?
I hope you said it’s NEUTRAL.
Why?
Because compounds are most
stable when they are neutral.
Binary Compound
What’s the formula for lithium nitride?
1. Find each element on the periodic table.
2. Determine the oxidation numbers (ion
charges) Li 1+ and N 33. Balance the ion charges. 3 Li 1+ = 1 N 34. Write the formula, positive ion before
negative. Make sure you write the numbers
in subscript.
Li3N
Naming Binary Compounds
Now let’s go backwards: NaCl as example
1. Write the name of the positive ion. Sodium
2. If that ion has more than one oxidation
number write it next to the name in Roman
numerals.
3. Find the root in the name for the negative
ion. Chlorine – Chlor
4. Add ide to the root Chloride
Practice
KBr
MgO
CaF2
Li2O
Ions with multiple oxidation
numbers
Name
Oxidation
Number
Copper (I)
1+
Copper (II)
2+
Iron (II)
2+
Copper (I) Chloride = CuCl
Iron (III)
3+
Cu+ and Cl-
Chromium
(II)
2+
Chromium
(III)
3+
Lead (II)
2+
Lead (IV)
4+
Some elements form more than one
type of ion with different charges and
so will combine with other ions in
different combinations.
Copper (II) Chloride = CuCl2
Cu2+ and
2 Cl-
Polyatomic Ions
Charge Name
Formula
1+
ammonium
NH3+
1-
Acetate
C2H3O2-
Some common ions contain
more than one atom.
Poly-many
Chlorate
ClO3-
The formula for sodium
carbonate
Hydroxide
OH-
Na +
Nitrate
NO3-
2-
3-
Carbonate
CO32-
Sulfate
SO42-
phosphate
PO43-
and CO32-
You need 2 Na + to make the
compound neutral
Na2 CO3
Hydrates
Hydrates are compounds with water bound to
them.
1. Name the ionic compound.
2. Then name by the number of water
molecules using hydrate
CaSO4·2H2O
Calcium sulfate dihydrate
Covalent Compounds
Relax, now this should be much easier, once you
remember these prefixes.
Number of atoms
Prefix
1
mono-
2
di-
3
tri-
4
tetra-
5
penta-
6
hexa-
7
hepta-
8
octa-
Covalent Compounds
Remember, in many covalent compounds the
elements are close to each other on the
periodic table. For instance, Nitrogen and
Oxygen
Here are the steps:
1. Add the appropriate prefix to the first
element.
2. Add the appropriate prefix to the second
element and make sure it ends in “ide”.
Covalent Compounds
NO
Nitrogen oxide or nitrogen monoxide
N2O Dinitrogen oxide
NO2 Nitrogen dioxide
N2O5 Dinitrogen pentoxide