1. Unit 6 Bonding
How elements interact.

2. The Octet Rule Atoms bond when their valence electrons interact.
Atoms bond to obtain a complete outer shell of 8 electrons. (Hydrogen and helium only need 2 outer electrons.) In this configuration they are stable.
Energy is stored in chemical bonds. When you break a bond, energy is absorbed. When you form a bond, energy is released.

3. Ionic Bonds Formed between metals and nonmetals.
Ionic bonds are formed by the transfer of electrons.
The resulting negative and positive ions are held together by electrical attraction.
Atoms on opposite sides of the periodic table are likely to form ionic bonds. Metals lose, nonmetals gain.
Examples:NaCl
CaF2

4. Metallic Bonds
Metals, like copper or gold, form metallic bonds between their atoms.
In metallic bonds the electrons are free to move from atom to atom.
In other words a sea of electrons surrounds the atom.
This explains why metals conduct electricity.
This also explains why metals are ductile and malleable. The atoms can slide past each other without breaking bonds.

5. Covalent Bonds Covalent bonds are formed by the sharing of electrons.
Covalent bonds are formed between non-metal atoms.
A double bond is formed if 2 pairs of electrons are shared. Examples of compounds with double bond are: O2 and CO2
A triple bond is formed if 3 pairs of electrons are shared. Examples of compounds with triple bonds are: N2.

6. Covalent Bonds con.
Atoms do not share electrons equally. When one atom attracts the electrons more than the other the bond is called polar covalent.
Elements in the upper right hand corner of the periodic table, excluding the noble gases, usually have the greater attraction for electrons. Fluorine will attract electrons more than any other element.

7. Covalent Bonding
Below is a Lewis dot diagram for Cl bonded to Cl to form a diatomic compound Cl2.
Cl atoms are sharing the one pair of electrons.

8. Hydrogen Bonding
Hydrogen bonding is an example of a strong intermolecular force. It is the strongest of all the bonds.
Why do you think this would be a strong bond? (Hint: think about electronegativity differences.)
What are the three molecules that bond with hydrogen to make hydrogen bonds?

9. Compounds
A compound consists of two or more elements chemically bonded together.
Differences between compounds and mixtures.
Compounds Mixtures
bonded not bonded
definite proportions varying proportions
2 or more elements contains elements/cmpds
definite properties properties vary w/ compo
chemical formula no chem formula

10. Chemical Compounds
Chemical formulas can be written for compounds. The chemical formulas give the elements and their proportions:
Ex. H2O Contains 2 H atoms for every 1 O atom
A molecule is the smallest unit of a compound that still has the properties of that compound.
Chemical formulas show the molecule’s structure or arrangement of atoms. This is very important for biological and pharmaceutical companies.

11. Structure and Properties
Ionic Solids:
Ions held together by the strong attraction of opposite charges.
Occur when metals are bonded to nonmetals.
Have a crystalline structure
High melting and boiling points
Poor conductors of electricity in the solid state because the charged ions are rigid in place.

12. Ionic Solids con.
In aqueous solutions the ions separate and are free to move. This makes their aqueous solutions good conductors of electricity.
They will also conduct electricity when melted.
Examples: NaCl
NaF
CaF2

13. Network Solids
A large network of atoms covalently bonded together in a fixed pattern.
The bonds are very strong
The resulting solid is strong and hard
They are poor conductors
High melting and boiling points b/c the bonds are hard to break.
ONLY 2 Examples: diamond = carbon and SiO2 = quartz

14. Molecular Substances Made up of molecules
Can be gases, solid or liquid
Relatively low melting and boiling point
Poor conductors
Examples: H2O, CH4, sugar C11H22O11

15. Polyatomic Ions – TABLE E!!
Some compounds have both ionic and covalent bonds. Ex: NaOH
The covalently bonded ions form a unit called a polyatomic ion.
A polyatomic ion contains two or more covalently bonded atoms
All the atoms share the charge of a polyatomic ion.
A polyatomic ion may bond with another polyatomic ion or a single “atom” ion. The resulting bond will be ionic.

16. Compound Names and Formulas
Naming ionic compounds
The name of the metal is listed first
The name of the nonmetal follows with its ending changed to –ide.
Indicate the oxidation state of transition metals by using roman numerals.
Ex: NaCl
Sodium chloride

17. Naming Polyatomic Ionic Compounds
4 Steps to Naming Polyatomic Ionic Compounds
Step 1: Write the name of the cation ion first
Step 2: Write the name of the polyatomic ion second
Step 3: Put them together to form a name
Step 4: Indicate the oxidation state of transition metals by using roman numerals
Example: Na2CO3

18. Naming Covalent Molecules
Use the following steps:
Step 1: Find the prefixes that correspond to the number of atoms present in the anion.
Mono – 1, di-2, tri-3, tetra – 4, penta – 5, hexa – 6, hepta – 7 , octa - 8
Step 2: Name the molecule with the cation first and add “ide” to the anion with the prefix

19. Converting an Ionic Compound Name to a Formula
List the symbols for each ion with the correct charge.
Write the symbols with the metal ion first.
“Criss-cross” the charges to determine the number of each ion that is required to make the compound neutral.
Check to be sure that the compound is neutral.
Ex: Aluminum fluoride Al+3F-1  AlF3

20. Polarity in Covalent Molecules
Electrons are not always shared ____________
______________________ will determine where the shared electrons spend ________ of their time
High electronegativity __________ the electrons _____________ that atom making the molecule ___________

21. Polar vs. Nonpolar Polar Molecules: Nonpolar Molecules:
Electron pairs are shared _______________
Molecules do not have _______________
Delta symbol helps show _______________
Nonpolar Molecules:
Molecules have ____________

22. Determining Polarity
Molecules are _______ when an atoms have ___________ in electronegativities greater than _____
Electrons __________ towards the atom with higher ________________________
Ex: Water
Oxygen is more electronegative than Hydrogen so the electrons stay mostly by O

23. Nonpolar Molecules
Electronegativities are the _________ on each end or the ___________ is less than _________
Oxygen atoms have an ___________ pull on the electrons causing ___________sharing between all atoms
Symmetry is __________