Chemical bonds
• A chemical bond is the force that holds atoms together
in a compound.
Chemical Formulas
• A chemical formula tells what elements a compound
contains and the exact amount of the atoms of each
element in a unit of that compound
• What elements and how many of each are in the
following?
• HCl (hydrochloric acid)
• CH3COOH (vinegar)
• C12H22O11 (sucrose)
Atomic Stability
• An atom is chemically stable when its outer energy level is full
• Octet rule: atoms tend to gain, lose or share electrons to have
eight electrons in their outer electron shell
• Which group of elements already has eight electrons in their
outer shell?
Ionic Bonds
Electron sharing
Ions
• An ion is formed when an atoms gains or loses an
electron.
• If it gains an electron it becomes negative
• If it loses an electron it becomes positive
Oxidation number
• Oxidation number tells you how many electrons an
atom has gained, lost, or shared to become stable
• Ionic compounds – same as the charge of the ion
“1 plus, 2 plus, 3 plus, SKIP, 3 minus, 2 minus, 1 minus ZIP”
Ionic Bond
• Ionic bond is the force of
attraction between the
opposite charges of the ions
• Forms between a metal and a
nonmetal
• Electrons are transferred
Writing Ionic Compounds
What is the chemical formula for Sodium and Oxygen?
Steps to take:
1. Determine atomic symbol and oxidation number for each element:
Sodium = Na1+
Oxygen = O22. “Swap and Drop” – The oxidation number becomes the subscript
for the other element
Na1+
O2Na2 O
3. Other things to know:
• Subscripts do not have a charge (so don’t write the + or -)
• You do not write “1” as a subscript – it is understood that there is
“1” there
• If the oxidations add up to zero then you just write the symbols, no
subscripts.
Practice writing formulas
1. Sodium and Chlorine
2. Potassium and Oxygen
3. Calcium and Fluorine
Writing names of binary ionic
compounds
1. Write the name of the positive ion
2. Write the root name of the negative ion. The root is the first part of
the element’s name.

Example: Chlorine would be chlor-
3. Add the ending –ide to the root.
 A few special elements:
Oxygen = oxide
Phosphorus = phosphide
Nitrogen = nitride
Sulfur = sulfide
Important note: Subscripts do not become part of the name for ionic
compounds.
Practice Naming Ionic Binary
Compounds
1. NaCl
2. K20
3. Calcium and Fluorine
4. MgO
Binary Compounds=compounds made of 2 elements
Transition Metals
0 Transition metals have more than 1 oxidation number
and this must be described in the compound name.
0 Use parentheses to tell which form of the element you
are talking about.
0 Copper + 3 + oxygen = copper (III) oxide
0 Copper +4 + oxygen = copper (IV) oxide
0Oxidation number = number of
electrons
0Subscript = number of atoms
More Hints- Ionic Compounds
0 Most compounds are binary.
0 Write the full name of the cation (positive ion) and the
root of the anion (negative ion)
0 Charges must = 0
0 Oxidations number are indicated by Roman numbers
in the names
Cupper (II) chloride
Copper (I) chloride
Activity: Bond With a Classmate
0 Each blank should have different compounds.
0 You cannot bond with the same element twice.
0 Work together to figure out how to do that formula
and name.
0 If you simply copy the answer you will not understand
what to do.
0 You have 10-15 minutes to complete each section.
0 Bring to me to spot check when done.
0 Sit down and wait.