6.2 Continued

1
6.2 ContinuedPolar Bonds!

• Key Concepts
• What happens when atoms dont share electrons
  equally?
• What factors determine whether a molecule is
  polar?
• How do attractions between polar molecules
  compare to attractions between nonpolar molecules?

2

• In general, atoms on the _______ side of the
  table have a greater attraction for electrons
• _____________ is the most electronegative element
• Why are the noble gases crossed off?

right
fluorine
Their outer energy levels are full
3
Unequal Sharing of Electrons

• Because some atoms are better at attracting
  electrons than others, sometimes electrons are
  shared _________________

unequally
In hydrogen chloride, which atom looks like it
has more electrons around it? These atoms
acquire ____________ charges
H
Cl
d
d
chlorine
HCl
partial
4
Unequal Sharing of Electrons

• When atoms share electrons ________________, the
  covalent bond is called a ______________ covalent
  bonds

unequally
polar
Polar means opposite in character
d
H
Cl
d
HCl
5
Unequal Sharing of Electrons

• This is similar to the polar bear and the
  penguinwho has the ice cream more often?

The polar bear (chlorine)
d
H
Cl
d
HCl
6
Unequal Sharing of Electrons

• If this was an ionic bond, how would the picture
  be different?

The penguin would GIVE AWAY the ice cream
No sharing!
7
Electronegativity Table

• Bond types can be determined by calculating the
  ______________ in the bonded atoms
  electronegativity values
• Nonpolar covalent
• less than 0.5
• Polar covalent
• 0.5 to 2.0
• Ionic
• greater than 2.0

difference
8
Electronegativity Table

• What type of bond is H H ?
• Nonpolar covalent
• less than 0.5
• Polar covalent
• 0.5 to 2.0
• Ionic
• greater than 2.0

2.1 2.1 0
nonpolar covalent
9
Electronegativity Table

• What type of bond is C O ?
• Nonpolar covalent
• less than 0.5
• Polar covalent
• 0.5 to 2.0
• Ionic
• greater than 2.0

3.5 2.5 1.0
Polar covalent
10
Electronegativity Table

• What type of bond is Na Cl ?
• Nonpolar covalent
• less than 0.5
• Polar covalent
• 0.5 to 2.0
• Ionic
• greater than 2.0

3.0 0.9 2.1
Ionic
11
Unequal Sharing of Electrons

• Polar and Nonpolar Molecules
• When a molecule has more than two atoms, two
  factors will determine whether or not the
  molecule is polar
• ________ of atoms
• ____________ of the molecule

type
shape
12
Unequal Sharing of Electrons

• In a carbon dioxide (CO2) molecule, the polar
  bonds ______________ out because the molecule is
  straight in shape or _________________.
• So this entire molecule is considered
  ________________
• Kind of like a game of tug-o-war that ___________
  is winning

cancel
d
d -
d -
linear
O C O
nonpolar
3.5 2.5 3.5
no one
13
Unequal Sharing of Electrons

• In a water (H2O) molecule, the polar bonds do
  ________ cancel out because the molecule
  is___________.
• Or in other words, one side of the water molecule
  is still partially ________________ while the
  other side is still partially _________________

2.1 H
2.1 H
NOT
d
d
bent
d
positive
O 3.5
negative
14
Attraction Between Molecules

• Polar molecules, due to their opposite charges,
  can also attract ________ _______________ and
  form additional bonds
• Due to the attraction between polar molecules,
  water exhibits
• ___________ tension
• a __________ boiling
• point than other molecules
• similar to it in size

one
another
surface
higher
15
Surface Tension
16
Attraction Between Molecules

• The attractions between polar molecules are
  _______________ than the attractions among
  nonpolarbut nonpolar attractions do ____________
• They explain why CO2 and N2, both normally
  __________, can be stored as solids or liquids at
  ___________ temperatures and ___________
  pressures

stronger
exist
gases
lower
higher
17
Assessment Questions

• What is the difference between a polar and
  nonpolar molecule?

Partial opposite charges
Partial charges cancel out
18
Assessment Questions

• What determines whether a molecule is polar?
• type of atoms and shape of molecule
• mass of atoms and number of valence electrons
• type and mass of atoms
• ionization energy and number of covalent bonds

19
Assessment Questions

• Why does water have a much higher boiling point
  than methane?
• Methane molecules are more polar, so its
  molecules have stronger attractive forces.
• Partial charges on the polar water molecules
  increase attractive forces between molecules.
• A water molecule has much more mass than a
  methane molecule, so water has a higher boiling
  point.
• Water has a higher boiling point because its
  molecules do not contain carbon atoms.