1. Count the number of atoms in each of the following compounds:
Thursday, October 30, 2014
Objective: Students will use the Criss-Cross Method to write Type I Formulas.
Warm-Up
Count the number of atoms in each of the following compounds:
H2CO3
4Fe(HCO3)3
2NH4NO3
Agenda
Ionic Bonds Notes
Writing Type I Formulas using Puzzle Piece Manipulatives

2. Introduction to Types of Bonds

3. Types of Bonds Ionic Bond Covalent Bond Metallic Bonds
Polar and Non-polar
Metallic Bonds

4. Ions Remember: an ion is an atom that has lost or gained electrons!
A positive ion is called a cation (lost electrons)
A negative ion is called an anion (gained electrons)
In your notes, find the charge of the following ions: Ca P Br Cs

5. Ionic Bonds
Once an ion has a charge, it will bond with other ions that have an opposite charge.
Ex: Na+ Cl- = NaCl
This is called an Ionic Bond. An ionic bond is the transfer of electrons from one element to another. This allows both atoms to end up with a more stable electron arrangement.
Ionic bonds occur between metals and non-metals.
A compound that results from an Ionic bond is called a salt.
Remember: The entire compound needs to be neutral (have no charge), therefore, the positives must equal the negatives.

6. Properties of Ionic Compounds
Form crystal structures at room temperature
Relatively high melting and boiling points
Conduct electricity when liquid or in a solution but NOT when in solid state

7. Covalent Bonds
Covalent bonds occur when electrons are shared between one or more elements.
Covalent bonds occur between a non-metal and a non-metal.
A compound that results from a covalent bond is called a molecule.

8. Properties of Covalent Compounds
Soft-tend to be gases, liquids or soft solids
Poor conductors of heat and electricity
Brittle or break rather than deform
Nonelectrolytes-do not conduct electricity in water

9. How to Tell the Difference
Determine if the first element is a metal or non- metal.
Determine if the second element is a metal or non- metal.
Determine if the compound is ionic or covalent.
Label the compound as a salt or a molecule.

10. Element 1 (metal or non-metal) Element 2 (metal or non-metal)
Examples
Compound
Element 1 (metal or non-metal)
Element 2 (metal or non-metal)
Bond Type
Salt or Molecule
Ca3P2
CO2
AlCl3
CrO
H2o

11. Brain Break: Show Me, Don’t Show Me

12. Electronegativity to Predict Types of Bonds

13. Definition
Electronegativity is the strength an atom has to attract electron pairs to itself.
The larger the value of electronegativity, the more strength an atom has to attract an electron pair.

14. Electronegativity values also tell us what will happen to the electrons in a bonding pair:
If the electronegativity values are the same (same atoms) or very small, the pairs will be shared equally; called a non-polar covalent bond.
If the electronegativity values are close, the electrons will shift towards the atom with the largest electronegativity value; called a polar covalent bond.
If the electronegativity values are far apart, the electron will transfer from one atom to the other; called an ionic bond.

15. Finding the Electronegativity: On Your Periodic Table
Find the electronegativity of the following atoms:
Calcium
Phosphorus
Vanadium
Bromine
Fluorine

16. Example Which of the following pairs is the most electronegative?
Sr or Si
Mg or Ru
O or F
Na or K
Ga or Sb

17. Example:
Arrange the following elements in order from lowest to highest electronegativity.
Al, N, Ti
Cr, Cl, P
Ba, B, C
As, Ni, Li

18. We can use electronegativity to predict what type of bond will form!
Use the periodic table to find the electronegativity values for each element.
Subtract the lowest electronegativity value from the highest electronegativity value.
The difference tells you what type of bond will form.
= non-polar covalent bond
= polar covalent bond
Greater than 1.5 = ionic bond

19. Examples Elements Difference Type of Bond C, Cl K, O H, B O, O
Electronegativity Element 1
Electronegativity Element 2
Difference
Type of Bond
C, Cl
K, O
H, B
O, O