#### Transcript Writing Formulas

```Writing Formulas
Oxidation Numbers & Chemical Formulas
Mrs. Wolfe
Vocabulary:
• Another word for Charge is
OXIDATION NUMBER.
Is there a pattern of Oxidation Numbers
on the Periodic Table?
•
•
•
•
•
•
•
•
What is the charge of a Hydrogen ion?
+ 1 (sometimes –1)
Lithium?
Also +1
Beryllium? Magnesium?
Both +2
Fluorine? Chlorine?
Both -1
• There IS a pattern! Let’s write that on
our Periodic Tables.
Common Oxidation Numbers
+1
0
+2
+3 NA -3 -2 -1
There are some Polyatomic Ions.
• Polyatomic Ions –
combination of elements
WITH A CHARGE!
• You will always have a
chart of their oxidation
numbers on a test/quiz.
• HERE COMES A
HANDOUT!
We can use oxidation numbers to
write formulas.
Remember, compounds must be
NEUTRAL.
Na
Cl
1
1
NaCl
Ionic Bonds & Formulas
• Write each ion, cation first.
polyatomic ion.
• Roman numerals = transition metal ion’s charge
Practice Problems:
• potassium + chlorine
K+ Cl-

KCl
• magnesium + nitrate
Mg2+ NO3-

Mg(NO3)2
• copper(II) + chlorine
Cu2+ Cl-

CuCl2
Time for a WS, then Labs!
• Qualitative Ion Testing Lab
• Formula of an Ionic Compound Lab
Some elements are diatomic.
The SEVEN diatomic elements
Br2 I2 N2 Cl2 H2 O2 F2
H
N O F
Cl
Br
I
Time for a WS, then GAMES!
• Formulas of Compounds WS
• Rummy!
Naming Ionic Compounds
• Write the names of both ions, CATION first.
• Change ending of ANION to -ide.
• Polyatomic ions have special names.
• Use Roman numerals to show the ion’s
charge if more than one is possible.
(Transition metals)
Practice Problems
• NaBr
– sodium bromide
• Na2CO3
– sodium carbonate
• FeCl3
– iron(III) chloride
Naming Covalent Compounds
1. Less e-neg atom
comes first.
2. Add prefixes to indicate # of atoms.
3. Change the ending of the
second element to -ide.
Molecular Prefixes
PREFIX
NUMBER
1
2
3
4
5
6
7
8
9
10
Practice Problems
• CCl4
– carbon tetrachloride
• N 2O
– dinitrogen monoxide
• SF6
– sulfur hexafluoride
Practice Problems
• arsenic trichloride
– AsCl3
• dinitrogen pentoxide
– N2O5
• tetraphosphorus decoxide
– P4O10
Let’s do a WS!
```