1. Chapter 6 p
Bonding

2. What is a Chemical Bond?
Chemical bonds provide the “glue” that holds all compounds together
An attraction between the protons of one atom and the electrons of another
What is the charge of a proton?
What is the charge of an electron?
The atoms will either SHARE or TRANSFER electrons
Different bonds account for different properties of a substance
The atoms will then have a complete outer shell and be STABLE, like a noble gas
The actual bond has stored (potential) energy
When a bond is broken, energy is absorbed
An ENDOTHERMIC process
When a bond is formed, energy is released
An EXOTHERMIC process
Remember, BARF!
Because of this, compounds have lower energy then the atoms themselves
This also causes the stability of the system to INCREASE

3. Examples: Broken or Formed? Absorbed or Released?
2H2 + O2 => 2H2O
NaCl => Na + Cl
4K + O2 => 2K2O
N + N => N2

4. Lewis Dot Diagrams- Atoms
Also called Electron Dot Diagrams
Find number of electrons in last energy level
Called the ?
Place the element symbol in the middle
Represents the atom and all of its full shells
Place dots, circles, or x’s all around the element symbol to represent the electrons
Start with 2 dots (if there are 2 valence electrons) on one side of the element symbol
Then 1 dot at each of the 3 other sides until the electrons are done
MAX is 8!
If there are still more electrons, make the rounds again.

5. Examples: Al Ca H Cl Ne

6. Lewis Dot Diagrams- Ions
The valence shell SHOULD be FULL!
Place the element symbol in the middle
Represents the atom and all of its full shells
Metals:
Lose valence electrons
Brackets around the symbol
POSITIVE charge outside the bracket
Non-Metals:
Gain valence electrons
Bracket and EIGHT DOTS around the symbol
NEGATIVE charge outside the bracket

7. Examples:
Na +
S -2
Mg +2
Cl -

8. Lewis Dot Diagrams- Compounds
Write the symbols of the 2 elements
Place the valence electrons around the symbols
Start with 2 at the top, then add one to each of the other sides until the valence is full
One element should have circles or dots
The other element should have x’s (usually)
Both elements should have FULL valence electron shells
Every TWO dots represent TWO electrons.
They can also be drawn as ONE line

9. Examples
Draw H2
Draw H2O
Draw CO2
Draw HCl

10. Open your book to p. 99 (1-5) 2 1 3

11. Now, open your book to p. 102 3
See Board 4

12. Octet Rule
Atoms will gain, lose, or share one or more valence electrons in order to achieve a complete outer shell of 8 VALENCE ELECTRONS
A complete octet of eight valence electrons results in an exceptionally stable electron configuration
This is why noble gases are so unreactive

13. There are 3 types of bonds that can be made:
Metallic
Ionic
Covalent

14. 1- Metallic Bonds Occurs ONLY in metals
Positive ions in a “sea” of mobile electrons
The negative electrons are attracted to the positive ion and that’s what holds the metal together
Properties of Metals (Metallic bonds)
Low ionization energy
Malleable and ductile
Because of moving valence electrons
Hard
Good conductors of heat and electricity
In a solid and a liquid
Because of MOBILE ELECTRONS
High melting and boiling points

15. Open your book to p. 103 3
2 (it’s a metal!) 1

16. Remember, Electronegativity
Atom’s attraction for electrons in a bond
Higher the electronegativity, the more the atom attracts electrons
Lower the electronegativity, the weaker is the attraction for electrons
Table S, Column 5
Measured on a scale of 0-4

17. Ionic or Covalent Bond To find out the type of bond that exists:
Look at the electronegativity for the 2 atoms bonding
Subtract their electronegativity
Absolute value!
If the EN difference is > 2.0 = IONIC
If the EN difference is < 2.0 = COVALENT

18. Ionic Bond: YES or NO Hydrogen and Chlorine Sodium and Chlorine
Potassium and Bromine
HBr HF
= 1.1 No
= 2.3 YES!
= 2.2 YES!
= 0.9 No
= 1.9 YES
Remember, If the difference is 2.0 or more, it is an ionic bond

19. 2- Ionic Bonds
Elements that form ionic bonds will try to achieve the OCTET RULE
Occurs between a metal and a non-metal
Formed when a metal transfers one or more electrons to a nonmetal
Metals lose e- and non-metals gain e-
Non-metals have higher electronegativities and will strip away e- from metals which have lower electronegativities

20. Ionic Substance Characteristics
They have IONIC BONDS
Hard
Good conductors of electricity ONLY when dissolved in water
In aqueous solution (aq) and a melted liquid (l)
NOT in SOLID form
Ions carry a charge and can’t move in a solid
High melting and boiling points
Due to the STRONG attraction of the ions

21. Ionic Character
To determine which compound has the greatest/ least ionic character, subtract the electronegativities of each element.
The compound that has the greatest EN difference = greatest ionic character.
The compound that has the smallest EN difference = least ionic character.

22. Ionic Substance Lewis Dot Diagrams
Metals
Write the Symbol of the Element
With brackets because its an ion
Look at the Oxidation Number
If there is more than one, look at the first one
Remember, that’s how many e- it will lose
Write the Oxidation number next to the Symbol
Nonmetals
Place a bracket [ ] around the symbol and the 8 dots
Remember, this is how many e- it will gain

23. Let’s do Some Examples Sodium Chloride Potassium Bromide
Hydrogen Fluoride
Magnesium Oxide
Na2O
CaCl2

24. Open your book to p. 110 (26-37) H h

25. Covalent Bonds Formed when two atoms SHARE electrons
NO TRANSFER OF ELECTRONS
Occurs between NON-METALS
Very STRONG bond
To find out if a covalent bond exists:
Subtract the electronegativity
If the answer is less than 2.0, it is a covalent bond

26. Covalent Bonds Character
Molecular substances (have covalent bonds):
Soft
Poor conductors of heat and electricity
There aren’t any charged particles to carry the electricity
Low melting points and boiling points
Remember the word “SPLash”
Opposite properties as an ionic bond

27. Covalent Bonds Atoms can share a number of electrons
More than just 2
Each pair of electrons that is shared, will form a bond
For example:
1 pair (2 electrons) = single bond
H - Br
2 pairs (4 electrons) = double bond
O = C = O
3 pairs (6 electrons) = triple bond
H - C = C - H

28. Covalent Bonds 3 types of covalent bonds: 1- Nonpolar covalent
Electrons are shared equally
EN difference between the elements is 0
Diatomic molecules
2- Polar covalent
Electrons are shared unequally
2 different non-metals
EN difference between
The element with the greater EN pulls stronger and gets a partial negative charge
WATER!!!!!!
3- Coordinate covalent
When one atom donates both of the electrons that are shared
NH3 plus H+ get you NH4+ (ammonium ion)
H2O + H+ -> H3O+ (hydronium ion)
Always has a charge

29. Lets do some examples: Cl2 H2S NH3 H2O NaCl NH4+
Tell me the electronegativity, the difference, the type of bond, and draw the structure
Cl2
H2S
NH3
H2O
NaCl
NH4+

30. Polar Character
To determine which compound has the greatest/least polar character, subtract the EN of each element.
The compound that has the greatest EN difference = most polar.
The compound that has the smallest EN difference = least polar.

32. Shape of Covalent Molecules
Non-Polar Molecules
Symmetrical
Looks the same!
Polar Molecules
Asymmetrical

33. Non-Polar Bonds and Non-Polar Shape
There are only ONE TYPE of molecule that can have a : Non-polar bond AND non-polar shape DIATOMIC MOLECULES!!!!!

34. Polar Bonds and Non-Polar Shape
UNEQUAL sharing of electrons, but SYMMETRICAL shape
CO2, CH4, CF4

35. Open your workbook up to p. 105-108 (13-25)

36. Summary of Bonds Ionic Transfer Electrons
Difference in electronegativity of 1.7 or more
Hard
Good conductors when melted or in an aqueous solution
Because of the movable ions
High melting and boiling points
Brackets!
Covalent
Share electrons
Difference in electronegativity of less than 1.7
Soft
Poor conductors of heat or electricity
Low melting or boiling points
SPLash
Different types of bonds

37. Summary of Bonds-Covalent
Nonpolar Covalent
Equally share electrons
Diatomic Molecules
Same electronegativies
Octet rule
Usually has symmetrical shape
Polar Covalent
Unequal sharing of electrons
Different electronegativites
Also, octet rule
Asymmetrical shape

38. Summary of Bonds Coordinate Covalent
One element donates BOTH electrons to the bond
Always will have a charge to it
Metallic Bonds
ONLY metals
Mobile electrons
Hard
Good conductors in a solid and liquid state
High melting and boiling points

39. STUDY FOR YOUR TEST!!! 