• Draw the Lewis structure for CO2
• Then use VSEPR theory to determine the 3D molecular shape of carbon dioxide.
Slide
1 of 47
Slide
2 of 47
• Ionic Bonds:
– electron transfer from metal to non‐metal forming ions
– opposites attract
• Metallic Bonds
– closely packed cations in a sea of valence electrons
Slide
3 of 47
Slide
4 of 47
• Covalent Bonds:
– The sharing of electrons
– The octet rule is the driving force behind how they bond
Slide
5 of 47
Slide
6 of 47
Slide
7 of 47
8.4
Polar Bonds and Molecules
Snow covers
approximately 23 percent
of Earth’s surface. Each
individual snowflake is
formed from as many as
100 snow crystals. The
polar bonds in water
molecules influence the
distinctive geometry of
snowflakes.
© Copyright Pearson Prentice Hall
Slide
8 of 47
12. Describe how differences in electronegativity values between atoms determine the bond type. Learn the scale: 0.0‐0.4 = nonpolar covalent, 0.4‐2.0 = polar covalent, ≥ 2.0 = ionic 13. Describe three types of intermolecular attractions and compare the strength of intermolecular attractions to ionic and covalent bonds.
14. Describe network solids and explain why network solids have very high melting points.
Slide
9 of 47
• Bond Polarity
– Is caused by unequal sharing of electrons in a bond
– Nonpolar covalent bond
• atoms in a bond share the electrons equally
• always happens in diatomic molecules of the same element – N2, O2
Slide
10 of 47
– Polar covalent bonds: the unequal sharing of electrons
• The more electronegative atom pulls the electrons closer to itself resulting in it having a slight negative charge. • The other atom in the bond will end up with a slight positive charge.
• The higher the electronegativity of an atom the greater its power in the tug‐of‐war with other atoms over electrons
Slide
11 of 47
8.4
Polar Bonds and
Molecules
>
Bond Polarity
The bonding pairs of electrons in covalent bonds
are pulled by the nuclei.
Slide
12 of 47
© Copyright Pearson Prentice Hall
8.4
Polar Bonds and
Molecules
>
Bond Polarity
The chlorine atom attracts the electron cloud
more than the hydrogen atom does.
Slide
13 of 47
© Copyright Pearson Prentice Hall
• The Greek letter delta is used to show that atoms involved in the bond acquire only partial
charges
Slide
14 of 47
• The O‐H bonds of water are polar
– The very electronegative oxygen pulls the bonding electrons away from hydrogen
– The O atom has a partial negative charge, the 2 H atoms have a partial positive charge
Slide
15 of 47
• Determining Bond Types
– The difference between the electronegativities of two atoms determines bond type: (learn these values)
0.0 – 0.4 = nonpolar covalent
0.4 – 2.0 = polar covalent
>2.0 = ionic
Slide
16 of 47
8.4
Polar Bonds and
Molecules
>
Bond Polarity
Slide
17 of 47
© Copyright Pearson Prentice Hall
Bond Types
Look at the chart on page 177 and determine the type of bond that will form between the two atoms: Li, F
A. non‐polar covalent
B. polar covalent
C.
ionic
Slide
18 of 47
© Copyright Pearson Prentice Hall
Bond Types
Look at the chart on page 177 and determine the type of bond that will form between the two atoms: C, O
A. non‐polar covalent
B. polar covalent
C.
ionic
Slide
19 of 47
© Copyright Pearson Prentice Hall
Bond Types
Look at the chart on page 177 and determine the type of bond that will form between the two atoms: H, P
A. non‐polar covalent
B. polar covalent
C.
ionic
Slide
20 of 47
© Copyright Pearson Prentice Hall
Bond Types
Look at the chart on page 177 and determine the type of bond that will form between the two atoms: Cl, Br
A. non‐polar covalent
B. polar covalent
C. ionic
Slide
21 of 47
© Copyright Pearson Prentice Hall
Bond Types
Determine the type of bond that will form between the two atoms: H, Cl
A.
non‐polar covalent
B.
polar covalent
C.
ionic
Slide
22 of 47
© Copyright Pearson Prentice Hall
Bond Types
Look at the chart on page 177 and determine the type of bond that will form between the two atoms: Na, Cl
A. nonpolar covalent
B. polar covalent
C.
ionic
Slide
23 of 47
© Copyright Pearson Prentice Hall
• Polar molecules
– The presence of a polar bond often makes the entire molecule polar
– exceptions • linear molecules around a central atom – the polarities cancel
• CO2
Slide
24 of 47
Slide
25 of 47
Polar Bonds and
Molecules
>
Polar Molecules
Animation 10 Learn to distinguish between
polar and nonpolar molecules.
Slide
26 of 47
© Copyright Pearson Prentice Hall
• Intermolecular attractions
– the attractions between molecules
– weaker than ionic or covalent bonds
– determine whether molecular compounds are solids, liquids or gases
• strong intermolecular attractions = solid
• weak intermolecular attractions = gas
Slide
27 of 47
– Types:
1. Van der Waals forces: 2 types
– Dipole interactions
• occur when polar molecules attract each other
– Dispersion forces
• the weakest of all molecular interactions
• caused by the motion of electrons
Slide
28 of 47
8.4
Polar Bonds and
Molecules
>
Polar Molecules
A hydrogen chloride molecule is a dipole.
Slide
29 of 47
© Copyright Pearson Prentice Hall
8.4
Polar Bonds and
Molecules
>
Attractions Between Molecules
Dipole interactions
occur when polar molecules are attracted to one another.
Slide
30 of 47
© Copyright Pearson Prentice Hall
• Dispersion forces may occur when transiently positive and negative regions of molecules attract each other, helping this Gecko walk up walls
Slide
31 of 47
2. Hydrogen bonds
• The partial positive charges of the H atoms in polar bonds are attracted to the lone pairs of e‐’s of other atoms
• strong intermolecular attractions
• accounts for water’s many amazing properties
Slide
32 of 47
8.4
Polar Bonds and
Molecules
>
Attractions Between Molecules
Hydrogen Bonding in Water
Slide
33 of 47
© Copyright Pearson Prentice Hall
8.4
Polar Bonds and
Molecules
>
Attractions Between Molecules
The relatively strong attractive forces between
water molecules cause the water to form small
drops on a waxy surface.
Slide
34 of 47
© Copyright Pearson Prentice Hall
• Properties of covalent compounds
– varies according to type of intermolecular bond
– covalent compounds exist in all three physical states
– usually have a low melting point below 300 degrees C
– usually poor conductor of electricity
Slide
35 of 47
• Ionic compounds are held together by electrostatic forces between all of the ions in the crystal lattice
• Covalent compounds are held together by the intermolecular attractions
– except for . . . Slide
36 of 47
• Network solids
– diamonds, silicon carbide
– all the atoms are covalently bonded to one another • they are enormous single molecules
– extremely strong compounds with high melting and boiling points
Slide
37 of 47
8.4
Polar Bonds and
Molecules
>
Intermolecular Attractions and Molecular
Properties
Diamond is an example of a network solid.
Diamond does not melt. It vaporizes to a gas at
3500°C or above.
Slide
38 of 47
© Copyright Pearson Prentice Hall
8.4
Polar Bonds and
Molecules
>
Intermolecular Attractions and Molecular
Properties
Silicon Carbide is a network solid. It has a
melting point of about 2700°C.
Slide
39 of 47
© Copyright Pearson Prentice Hall
8.4
Polar Bonds and
Molecules
>
Intermolecular Attractions and Molecular
Properties
Slide
40 of 47
© Copyright Pearson Prentice Hall
8.4 Section Quiz.
In a molecule, the atom with the largest electronegativity value A. repels electrons more strongly and acquires a slightly negative charge.
B. repels electrons more strongly and acquires a slightly positive charge.
C. attracts electrons more strongly and acquires a slightly positive charge.
D. attracts electrons more strongly and acquires a slightly negative charge.
© Copyright Pearson Prentice Hall
Slide
41 of 47
8.4 Section Quiz.
When polar molecules are placed between oppositely charged plates, the negative A. molecules stick to the positive plates.
B. molecules stick to the negative plates.
C. ends of the molecules turn toward the positive plates.
D. ends of the molecules turn toward the negative plates.
© Copyright Pearson Prentice Hall
Slide
42 of 47
8.4 Section Quiz.
Which of the following bond types is the weakest?
A. ionic bond
B. Van der Waals force
C. covalent bond
D. hydrogen bond
Slide
43 of 47
© Copyright Pearson Prentice Hall
8.4 Section Quiz.
The polar molecule among the following is:
A. CCl4
B. CO2
C. H2O
D. N2
Slide
44 of 47
© Copyright Pearson Prentice Hall
8.4 Section Quiz.
The strongest intermolecular attractive forces from among those listed:
A. dispersion forces
B. dipole interactions
C.
hydrogen bonds
D. cannot be determined
© Copyright Pearson Prentice Hall
Slide
45 of 47
8.4 Section Quiz.
Network solids ____________
A. have low melting points
B. have low boiling points
C. are extremely stable, strong compounds
D. are generally ductile
Slide
46 of 47
© Copyright Pearson Prentice Hall
•
•
•
•
WS 8.4
Test Review Q’s
Review for the test, Notebook due before test
Slide
47 of 47