1. Chem I: Chapters 4, 5, 9 Chem IH: 7, 8, 9
Chemical Bonding
Chem I: Chapters 4, 5, 9
Chem IH: 7, 8, 9
Dfhaer

2. Unit Objectives To be able to:
Explain why some elements react (form bonds.)
Explain the difference between an ionic & a covalent bond.
Demonstrate e- reconfiguration when a simple compound is formed.
Explain how interparticle forces affect the properties of ionic & covalent compounds.

3. Sodium (metal) Solid Good conductor of electricity & heat
VERY reactive
Silvery/luster
Malleable, soft
Melting point-low 98 C
Uses: never pure in nature b/c sooooo reactive!

4. Chlorine (nonmetal) Poisonous, green gas Disinfectant
Reactivity-very reactive. Rarely found pure in nature b/c sooo reactive.

5. Salt (NaCl) Edible, common food additive White Crystalline solid
Reactivity-not reactive/ very stable
Brittle
Conductivity- as a solid, poor conductor
As a liquid or in aqueous solution, excellent conductor = ELECTROLYTE

6. Carbon (nonmetal) Solid @ room temperature
Fairly rm temperature. Very reactive at high temperatures.
Most of the compounds in living things made from carbon.
Brittle/hard (charcoal/diamond)
High melting & boiling points

7. Oxygen (Nonmetal) Gas at room temp Colorless, odorless, tasteless
21% of atmosphere
Very low MP/BP (-183 C BP)
Slightly soluble in water
Reactive, combines w/many elements
Most abundant element in earth’s crust

8. Carbon dioxide Somewhat soluble in water Poor conductor
Fairly unreactive
Uses
some fire extinguisher b/c it won’t burn
Photosynthesis
Nearly all the food for all living things comes thru photosynthesis
Trees pull CO2 out of the air & decrease greenhouse effect

9. Hydrogen Odorless, tasteless, colorless Very reactive (ex: Hindenburg)
Low MP & BP
Gas at rm temperature
Slightly soluble in water
not a conductor
Lightest and most abundant element in universe

10. Water Liquid at room temp Stable-doesn’t react w/most things examples
Chemical rxns in human body take place in water
`Necessary for photosynthesis

11. Classwork On p 59 of I.N. Analyze CO2
Compare the properties of C, O, and CO2

12. What is Happening? Watch the videos.
What is happening in all of these reactions?
Hydrogen balloon burning
2H2 + O2  2H2O
sodium metal & chlorine
Na + Cl  NaCl
sodium iodide & mercury (II) chloride
2NaI + HgCl2  2NaCl + HgI2

13. The Chemical Bond The force that holds two atoms together
Occurs using valence electrons

14. Lewis Dot Diagram
Definition: System of showing the valence e-s for an atom
Help us predict bonds

15. Lewis Dot Diagram, cont. 1) Element symbol in middle
2) Valence e-s represented by dots
Place v.e.-s around the element symbol in 4 locations
Above
Below
Left
Right
Don’t pair up any, until 1 in each location.

16. Lewis Dot Diagram, cont. Practice:
Together: let’s do LDD for Hydrogen, helium,
You practice: lithium, beryllium, boron, carbon, nitrogen, oxygen, fluorine, neon.

17. Lewis Dot Diagram of Main Group Elements

18. The Noble Gases All occur in nature
BUT no compounds containing them are ever found in nature
Common denominator is that they all have 8 valence e-s. (*except He, which has 2)
This is what makes them stable/unreactive
This is called “Noble Gas Configuration” (NGC)

19. All other elements “want” NGC, so they can be stable.

20. Atoms can Get NGC in one of 2 ways (cont.)
1. Lose/gain e-s (IONIC bond)
This occurs when the 2 atoms in the bond pull on their e-s w/different strengths
Big EN difference
Typically occurs btwn a _____ & a _____.

21. Atoms can Get NGC in one of 2 ways (cont.)
2. Share e-s (COVALENT bond)
This occurs when the 2 atoms in the bond pull on their e-s w/the same (or similar) strength
Small EN difference
Typically occurs between 2 ___________.

22. 3 “Classes” of Elements (Review- Do Not Copy)
Metals = pink
Conductors? Yes!
Hold e-s? Loosely
How many V.E’s? 1-3
Nonmetals = green
Conductors? No!
Hold e-s? Tightly
How many V.E.’s? 5-7
Metalloids = blue
“In between”

23. Ions & the Octet Rule
Ions are charged particles that have lost or gained e-s to satisfy the octet rule (8 e-s)
They will typically form based on what requires the smallest gain or loss of e-s to complete an octet.
Ex: Na  Na+ + e-
Ex: Cl + e-  Cl-

24. Formation of Ions
The charge on an ion is called its “oxidation number”

25. Formation of Ions, cont. Metals tend to lose electrons
Have + oxidation number
Called “cations”
Metal ions are given the element name
Ex: Na+ = “sodium ion”

26. Formation of Ions, cont. Nonmetals tend to gain electrons
Have – oxidation number
Called “anions”
Nonmetal ions are given the element name w/an “-ide” ending
Ex: O2- = “oxide ion”

27. TO DO: Label Your Periodic Table
Label Groups 1, 2, 3, 16, 17 w/the oxidation number of each group.
Group # Oxidation #
1 +1
2 +2
3 +3

28. Practice Together, write the arrow orbital diagram for a sodium atom.
Now draw the arrow orbital diagram for a sodium ion.
Identify the noble gas that has the same notation as a sodium ion.
Write the symbol for a sodium ion

29. Formation of an ionic bond
When e-s are lost by 1 atom they are gained by another. Therefore, cations & anions are formed at the same time.
Occur between elements w/great differences in EN.
Usually a metal & a nonmetal
Ex: Na & Cl

30. Formation of an ionic bond, cont.
Attraction between ions is what forms bond.
Cl-1 Na+1 Cl-1 Na+1 Cl-1
Na+1 Cl-1 Na+1 Cl-1 Na+1
Practice: Draw Lewis Dot Diagrams for sodium and chlorine ATOMS.
Then show what happens to form sodium & chlorine IONS.
(BONUS: What NG is each ion like?)

31. Formation of an ionic bond, cont.
Note: you will not always have a 1:1 ratio of + to - ions.
Ex: MgI2 -see next slide

32. Formation of MgI2 .Mg. + :I: → Mg.+ + :I: - (are they happy?)
.Mg. + :I: → Mg.+ + :I: - (are they happy?)
.Mg. + :I: :I: → Mg2+ + :I: :I:

33. ACTIVITY: Egg Carton Atoms Ionic Bonding
MATERIALS
Egg carton (“atom”)
Candy or marbles (“electrons”)
Data Sheet

34. Rules for “Placing” e-s
Place e-s in lowest available E.L.
Fill an E.L. before putting e-s in next available E.L.
Only 1 “electron” per space in egg carton.

35. Your Goal:”Happy” Atoms Ionic Compound
With your partner, obtain NGC for BOTH of your atoms!
Each atom will have EITHER
A full 1st E.L. & no e-s in 2nd E.L. OR
A full 1st and 2nd E.L.
One will donate e-s & one will receive e-s.

36. Step 1: Your Atom Count # of “e-s” Identify element
Identify column/group#
What is valence level?
How many valence e-s?
How many e-s must be gained to obtain NGC?
How many e-s must be lost to obtain NGC?
How many e-s lost or gained (Which is easier?)

37. Step 2: Both Atoms
Share your information with your partner & record on Data Table.
Decide how you can help each other obtain NGC by giving or receiving e-s.
Make the e- switch! & observe NGC.

38. Step 3: Discuss Results

39. Now it’s your turn! Partner 1: 3 e-s Partner 2: 9 e-s
(Identify your elements first.)
With your new set of “electrons,” form an ionic compound with your partner.
Record your data and your partner’s.
Be prepared to discuss.

40. Results of Example 2: Li & F

41. Summary so Far
Atoms that collide may bond if they can help each other become more stable.
Noble gases are stable the way they are-8 valence e-s in most cases (“octet”).
All other elements want to be like noble gases.
Two ways to get “NGC”
Transfer e-s if strength of 2 elements is very unequal (ionic bond)
Share e-s if strength of 2 elements is pretty equal (covalent bond)

42. “Isoelectronic”
Term used to describe atoms/ions with the same e- configuration
Ex: F- and Ne
Both have 2 e-s in the 1st energy level
Both have 8 electrons in the 2nd energy level
Ex: He and H-
Both have 2 electrons in the exact same arrangement

43. Formulas
Tell us:
the elements that make up the compound
the # of atoms of each element in a unit of the compound
The smallest unit of an Ionic Compound is called a “Formula Unit”
The smallest unit of a Covalent compound is called a Formula Unit or “Molecule”

44. To Explain Why…
Elements in an ionic compound occur in a specific ratio, BUT
You never have just 1 Na and 1 Cl, for example
Instead YOU HAVE A CRYSTALLINE STRUCTURE (“lattice”) (see p 134)

45. Crystal Arrangement Causes Behavior of Ionic Compounds
e Fig p 570
Each ion is “locked in” in 6 directions (ex: each Na+ is surrounded by 6 Cl-)
Giant Ionic Lattice
Rotating NaCl Lattice

46. Properties of Ionic Compounds
Brittle
Cubic in shape
Very stable
Solids (high MP, BP.)
Very soluble in water
Electrolyte

47. Ionic Compounds-Electrolytes
In order for something to be a good conductor, it must have freely moving charged particles.
Ions are charged particles that are “locked in” when in solid form…
BUT when they are melted or dissolved in water, BOY CAN THEY MOVE!

48. Interparticle Forces
The attraction between formula units (particles of a substance) is called: “INTERPARTICLE FORCES”
strong IP forces between adjacent NaCl units, for example.
weak attraction between adjacent molecules of covalent compounds, H2O, for example.

49. Interparticle Forces in Covalent Compounds
Molecules have little to no charge so they are attracted v. weakly to one another
This makes covalent compounds
Liquids/gases (almost always!)
Have low MP/BP

50. Interparticle Forces in Covalent Compounds, cont.
Not soluble in water (or very slightly) ex: oil, gas, CO2
poor conductors-WHY??? Think-Pair-Share!!!

51. Why covalent compounds are lousy conductors.
In order for something to be a conductor, it must have freely-moving charged particles.

52. Types of Covalent Bonds
Single Bond- When a pair of electrons is shared
Double Bond….you tell me!
Triple Bond…

53. Examples of Covalent Compounds
The properties of covalent compounds vary more widely than those of ionic cpds.
Ex: butter, water, CO2, gasoline, candle wax, table sugar, alcohol

54. Activity: Egg Carton Atoms Covalent Bonding
Your Goal: With your partner, obtain NGC for both your atoms by sharing electrons!
NOTE: Overlap cartons to represent sharing of e-s.

55. Practice Together: H2 Each partner is going to represent a H atom.
Let’s answer the Qs together.

56. Step 2: Both Atoms Remove “e-s” from rows that will be overlapped.
Overlap 1 carton’s row/s with your partner’s.
Place the removed e-s from both atoms in the overlapped rows. -NGC!

57. Step 1: Your Atom, F Count # of “e-s” Identify element
Identify column/group#
What is valence level?
How many valence e-s?
How many e-s must be gained to obtain NGC?
This is the # of rows that must be overlapped to share e-s with your partner.

58. Step 2: Both Atoms Remove “e-s” from rows that will be overlapped.
Overlap 1 carton’s row/s with your partner’s.
Place the removed e-s from both atoms in the overlapped rows. -NGC!

59. Solution

60. More Practice Each person makes their atom.
Next form covalent compound with neighbor.
Oxygen
Nitrogen

61. Answers to practice
Oxygen involves the overlap of 2 rows in each carton. (double bond)
Nitrogen involves the overlap of 3 rows in each carton. (triple bond)

62. Quiz Ionic bonds are formed by the ______ of electrons.
Covalent bonds are formed by the ________ of electrons.
CO is a/n ionic/covalent compound.
NaF is a/n ionic/covalent compound.