1. Bonding
Chapter 7
(Page 196)

2. Essential question:
Why is chemical bonding important and how can chemist predict what types of bonds will occur in a chemical reaction?

3. Vocabulary: Section 1 Bonding Polarization Electronegetivity
Ionization energy
Nonpolar covalent bond
Ionic bond
Metallic bond
Polarize
Electrostatic force

4. Compounds, not elements, determines most of what we experience in this world
How elements bond together in compounds determines the properties of matter that we observe
Many of the elements that we observe in nature are poisonous in their natural form, but as compounds, they sustain and enable life
Ionic compounds, unlike covalent compounds, dissociates in water to form positive and negative ions
Covalent compounds remain as whole units when dissolved in water
Metals form special bonds that are neither ionic or covalent, but somewhere in the middle
Metals conduct electricity because their valence electrons are not fixed and can move from atom to atom

5. Sulfur can help life because it is an essential nutrient and is found in amino acids
Sulfur also causes the foul smell in garlic, rotten eggs and in skunks
Iron is important to many body functions including the transferring of oxygen from lungs to the cells (hemoglobin)
Iron is also magnetic in nature and when the two (iron and sulfur) are mixed they each maintain their physical and chemical properties, until both are heated close to the melting point of steel (where a chemical reaction occurs)
The resulting compound is iron sulfide and no longer has the properties of iron or sulfur, but new properties

6. What is a chemical bond?
Using a molecule building kit, a chemical bond is a stick and atoms joined together
The sticks between the atoms represent bonds between each atom
Inside the atom are positive and negative charges that attract and repel each other (protons repel other protons and electrons repel each other)
There are also intermolecular forces, forces between one atom and another atom or atoms
Because of protons of one atom attracting electrons of another atom, there is an array of charges that each atom has to deal with which can cause a shift in atomic charges
Polarization is an uneven distribution of positive or negative charge that occurs when anything (like other atoms) creates an charge outside of the atom (this is how bonds form)

7. That distortion is called polarization.
The electron cloud responds to changes in the electromagnetic environment.
That distortion is called polarization.

8. What happens when two hydrogen atoms approach each other?
Each nucleus attracts the electron cloud of the other atom.
Each nucleus repels the other nucleus.
The electron cloud repels the other electron cloud.
At a certain distance there is an equilibrium between attractive and repulsive forces.

9. In nonpolar covalent bonds, the difference between the electronegativity of both atoms is very little (between 0.3 and 0.0)
In polar covalent bonds the difference between the electronegativity of both atoms is a moderate difference (between 1.7 and 0.3)
In ionic bonds the difference between the electronegativity of both atoms is a large difference (between 3.3 and 1.7)

10. Covalent bond is formed when atoms share electrons (sometimes the sharing is equal, sometimes it is not equal sharing)
Ionic bonds are formed when metals give 1, 2, or three electrons to a nonmetal (each atom becomes charged (as positive or negative)
In a non-polar covalent bond, the sharing of electrons is equal so the electrons are evenly distributed so there is little charge separation on the surface of the molecule
In a polar covalent bond, the uneven sharing of electrons creates a region that is more positive, and another area that is more positive than the opposite end.
Metallic bonds both atoms have a low electronegativity and low ionization energy so they don’t attract each other’s electrons very well
As a result of metallic bonding, a bunch of atoms share electrons

11. Assignment Take a new sheet of paper and fold it into three sections
Write your name, the title of the chapter and the number
On the first section from the sheet of paper, please write six things that you learned from your notes so far that could appear on your test.

12. Sometimes when two or more molecules combine the result can be a polar or non polar molecule, even though individual bonds are polar
The reason for this is because when a molecule is called polar, the overall molecule is polar and not just certain bonds (the surface of the molecule can be non polar, even though is has polar bonds)

13. When a chemical bond is formed, some valence electrons are either shared or transferred between atoms
Only unpaired unshared electrons can participate in chemical bonds
It is important to know that in the outer shell, the 5th, 6th and 7th valence electrons pair up and reduce the amount of electrons available to take part in chemical bonding
The number of valence electrons affects bond number and ion charge
In a molecular compound, each unpaired unshared valence electron can form one covalent chemical bond
Example: both nitrogen and phosphorous atoms have three unpaired valence electrons (so they can form three covalent bonds)
All atoms react chemically to reach the octet configuration

14. Atoms are neutral charge but unpaired unshared electrons can cause atoms to become positive or negative ions by the gaining or loss of electrons
When an atom (metal) loses one or more electrons, it becomes a positive ion with a “+” 1, 2, or 3 charge
Group 1 metals lose 1 electron to become a +1 ion
Group 2 metals lose 2 electron to become a +2 ion
Group 13 metals lose 3 electron to become a +3 ion
When an atom (nonmetal) gains one or more electrons, it becomes a negative ion with a “-” 1, 2, or 3 charge
Group 17 metals gain 1 electron to become a -1 ion
Group 16 metals gain 2 electron to become a -2 ion
Group 15 metals gain 3 electron to become a -3 ion

15. A covalent bond An ionic bond
Electrons are shared between the two nuclei.
One or more electrons are transferred to form ions.
The positive and negative ions attract each other.

16. Some atoms are more greedy for electrons than others!
Electrons are unevenly shared between oxygen and hydrogen.

17. Oxygen is slightly more electronegative than hydrogen.
Electronegativity
(electron sharing)
Oxygen is slightly more electronegative than hydrogen.
This results in uneven sharing of electrons.

18. Types of bond Nonpolar covalent bond Polar covalent bond Atom 1 Atom 2
Ionic bond
Atom 1
Atom 2
Difference in EN
Electron sharing
high EN
very little
equal or nearly equal sharing
high EN
medium EN
moderate
uneven sharing
high EN
low EN
large
transfer of electrons
EN = electronegativity

19. Types of bond

20. Types of bond
An ionic crystal
Ionic bonds connect atoms to all neighbors, not just a single neighbor as in a molecule.

21. Types of bond A metallic bond Like a covalent bond
Like an ionic bond
Electrons are shared
No two atoms are specifically bonded together
metallic bond: an attraction between metal atoms that loosely involve many electrons.

22. Nonpolar covalent bond Polar covalent bond
Ionic bond
Difference in EN
Electron sharing
very little
equal or nearly equal sharing
moderate
uneven sharing
large
transfer of electrons
EN = electronegativity

24. Electronegativity of atoms:
Difference in electronegativity:
I – I = 2.66 – 2.66 = 0

25. Electronegativity of atoms: I = 2.66
Difference in electronegativity:
I – I = 2.66 – 2.66 = 0
The I–I bond is nonpolar covalent.

26. Difference in electronegativity: O – C = 3.44 – 2.55 = 0.89
of atoms:
C = 2.55
O = 3.44
Difference in electronegativity:
O – C = 3.44 – 2.55 = 0.89
The C–O bond is polar covalent.
0.89

27. Nonpolar bonds in a molecule make the molecule nonpolar.

28. Polar bonds in a molecule make the molecule polar.

29. Assignment
Write a three dollar summary of what you learned (a paragraph, with a topic sentence and three supporting sentences)
Turn to page 224 and complete # 1 – 5 then turn them in
Honors chemistry Homework:
Page 224 #

30. Vocabulary: Section 2 Octet rule Free radical Antioxident
Non-polar covalent
Ionic bond
Polar covalent bond

31. Ionic bonds

32. Ionic bonds Electron configuration of ions
Same configuration as neon (a noble gas)

33. Ionic bonds
Electron configuration of ions

34. Ionic bonds
Write the electron configuration for a magnesium ion (Mg2+).
Asked: Electron configuration of Mg2+
Given: Mg, atomic number of 12, charge of +2
Relationships: The electron configuration of magnesium is 1s22s22p63s2.

35. Ionic formulas
What is the correct formula for calcium oxide, a compound used in making paper and pottery, and adjusting the pH of soils?
Asked: The formula for the ionic compound calcium oxide
Given: Calcium oxide is made from calcium and oxygen ions. Calcium forms +2 ions and oxygen forms –2 ions.
Relationships: Ca2+ and O2– must combine in a ratio that will balance out the positive and negative charges.

36. As stated earlier, elements share, lose or gain electrons to satisfy the octet rule and become more stable
The exception to the octet rule are those closest to helium such a hydrogen, lithium, beryllium and boron (since helium is the closest completely stable noble gas
For those elements mentioned above, the octet rule is more the duel rule or the rule of “2” these elements bond chemically to have a configuration of two electrons

37. In a covalent bond, each shared electron is seen as a valence electron by both elements
In H2, each atom shares a electron to have two electrons in their outer shell
In water H2O, each the hydrogen shares an electron with the oxygen giving them two valence electrons and oxygen eight valence electrons
When ions are formed, they have an electron configuration of the closest noble gas
Na+ has the neon configuration
O2- has the Neon configuration

38. Covalent bonds

39. Covalent bonds
Bonds form in such a way that each atom in the compound achieves the same number of valence electrons as the closest noble gas atom.

40. Covalent bonds Ion formation
Electrons are transferred so that each element has 8 valence electrons and has the same configuration as the closest noble gas. The light elements H, Li, Be, and B prefer to have 2 valence electrons.
Ion formation
Atoms gain or lose one or more electrons to reach the same electron configuration as the closest noble gas, with 8 valence electrons.
octet rule: rule that states that elements transfer or share electrons in chemical bonds to reach a stable configuration of eight valence electrons.

41. Assignment
On the second section of that sheet of paper, please write six things that you learned from your notes so far that could appear on your test.

42. Ionic compounds generally form crystals because of the interchanging of +tive and –tive charges
Ionic compounds are neutral even though they are made up of trillions of charged ions
The formula of an ionic compound can be determined as long as you cancel the positive and negative

43. As stated earlier, covalent bonds share electrons not transfer them
The number of covalent bonds is equal to the number of unpaired valence electrons
Only hydrogen and nonmetals are commonly found as covalent bonds
Carbon-like compounds form four covalent bond
Nitrogen-like compounds form three covalent bond
Oxygen-like compounds form two covalent bond
Halogens form one covalent bond

44. Carbon has four valence electrons and they are all unpaired
Oxygen has six valence electrons, but only two are unpaired and able to form covalent bonds
If Lewis dot structures are drawn for elements, it can be used to tell the valence electrons and the unpaired electrons (which is the same as the number of possible covalent bonds)
Atoms or molecules with unpaired electrons are highly reactive and are known as free radicals
Free radicals are responsible for aging, and diseases such as cancer
Antioxidants are a good part of diet because they prevent free radicals form reacting with and damaging DNA

45. Assignment
Write a detailed three dollar summary of what you learned (a paragraph, with a topic sentence and three supporting sentences)
Turn to page 224 and complete # 6 – 7,
Page 226 # then turn them in
Honors chemistry homework
Page 225 #

46. Vocabulary: Section 3 Isomer Free radical Antioxidant VSEPR
Region of electron density
Trigonal planar
Lone pairs
Tetrahedral
Trigonal pyramidal
Bent

47. Why can’t a water molecule be like this?
Each water molecule contains one oxygen atom and two hydrogen atoms.
One central oxygen atom
Why can’t a water molecule be like this?
One hydrogen atom on either side

48. Why can’t a water molecule be like this?
The oxygen forms one bond
One hydrogen forms two bonds
One hydrogen forms one bond
The Lewis structures indicate that it is not possible
Why can’t a water molecule be like this?

49. Lewis structures for individual atoms are like puzzle pieces.
Put them together to form molecules.

50. Use Lewis structures to predict:
1) the chemical formula
2) the bonding pattern
3) the shape of the molecule
To be discussed
later in this section
H2O is flat and bent

51. Lewis Dot Structures
Lewis dot structures allows chemist to be able to identify and predict how elements will join together to form molecules
If you have a formula, you can use Lewis structures to determine how they will join
The goal of using Lewis structures is to end up with each atom having no unpaired electrons and each having eight valence electrons (unless it is hydrogen, helium, lithium, beryllium or boron)

52. The chemical formula for water is H2O
Use Lewis structures to predict:
1) the chemical formula
The chemical formula for water is H2O
(2 hydrogen atoms for every 1 oxygen atom)

53. Isomers
Sometimes there is more than one way to satisfy the molecular formula
Isomers are when there is more than one way to represent a chemical formula
For example, C2H6O can form ethanol as well as dimethyl ether (they both have different chemical and physical properties)

54. Consider the chemical formula C2H6O
Ethanol

55. Consider the chemical formula C2H6O
Dimethyl ether

56. Two isomers of C2H6O
Ethanol
Dimethyl ether
isomer: a specific structure of a molecule, only used when a chemical formula could represent more than one molecule.

57. Give three isomers for the formula C3H8O
Give three isomers for the formula C3H8O. Show the Lewis dot diagram and the structural formula for each molecule.

58. Give three isomers for the formula C3H8O
Give three isomers for the formula C3H8O. Show the Lewis dot diagram and the structural formula for each molecule.
Asked: The Lewis dot diagrams and structural formulas for the three molecules represented by the formula C3H8O
Given: Carbon has four unpaired electrons, hydrogen has one, and oxygen has two. Three carbons, eight hydrogens and one oxygen form each molecule.
Relationships: The atoms will bond together such that all unpaired electrons will be paired up with electrons from other atoms.

59. Give three isomers for the formula C3H8O
Give three isomers for the formula C3H8O. Show the Lewis dot diagram and the structural formula for each molecule.
Asked: The Lewis dot diagrams and structural formulas for the three molecules represented by the formula C3H8O
Given: Carbon has four unpaired electrons, hydrogen has one, and oxygen has two. Three carbons, eight hydrogens and one oxygen form each molecule.
Relationships: The atoms will bond together such that all unpaired electrons will be paired up with electrons from other atoms.

60. Double and Triple Bonds
There are many compounds or molecules with more than one bond between two atoms
Ethene and ethyne have double and triple bonds respectively
Oxygen also has double bonds
Lewis dot structures show two dimensional representations of chemical bonding whit is a limitation since the 3D shape of a molecule determines the chemical properties of a molecule
VSEPR – Valence Shell Electron Pair Repulsion
The first three words “VSE” represent the valence electrons and how they react and the last two words “PR” represents the paired electrons that are not shared
Paired electrons are not shared in a chemical bond, but they do effect the shape of the molecule
Paired electrons repel each other as well as repel shared ones

61. Multiple bonds Sharing a pair of electrons is called a single bond.
Carbon, nitrogen and oxygen commonly form double and triple bonds.
Double bond
(2 pairs of electrons)
Triple bond
(3 pairs of electrons)
Ethene
Ethyne

62. Assignment
On the third section of that sheet of paper, please write six things that you learned from your notes so far that could appear on your test.

63. Electron Density
If you rubbed a balloon against your hair, it would pull electrons off of your hair and become more negative
If you put two charged balloons together, they would repel each other (since similar charges repel)
The same thing happens when there are two regions of electron density around the atom
The electrons repel each other until they are the maximum distance apart
When you have two balloons that are negatively charged, they move apart in a linear shape apart (180o)
When they are three areas, the shape of the repulsion (120o) which is called trigonal planar shaped
When they are four areas, the shape of the repulsion (109.5o) which is called tetrahedral shaped

64. VSEPR theory
Molecular polarity is an uneven distribution of molecular charges between atoms
VSEPR stands for valence-shell, electron-pair repulsion
VSEPR theory states that repulsion between the sets of valence electrons surrounding an atom causes these sets

65. Two areas of electron density repel to form linear shapes
Two regions
Two areas of electron density repel to form linear shapes
The two 180o angles formed around each carbon make the entire molecule straight.

66. Three areas of electron density repel to form trigonal planar shapes
Three regions
Three areas of electron density repel to form trigonal planar shapes
These three regions of electron density repel, forming 120o angles between the three atoms bonded to each carbon atom

67. Four regions
The four regions of electron density around the carbon repel, forming angles of 109.5o.

68. Four regions
Different geometries formed by atoms with four regions of electron density
Tetrahedral
Trigonal pyramidal
Bent

69. Water and ammonia have similar angles even though they are not the same.

71. Assignment
Write a detailed three dollar summary of what you learned (a paragraph, with a topic sentence and three supporting sentences)
Turn to page 224 and complete # 8 – 14 then turn them in
Honors chemistry homework
Page 225 #

72. Test: - Next week Tuesday or Thursday depending on your class.
Homework requirement: Learn all terms and concepts covered on this topic.
Make sure you have all assignments between page 224 and 227 completed and turned in by your test date.