polarity

• What causes polar bonds in molecules?

  Differences in electronegativities
• In a bond between two unlike atoms, what happens to the electron pair?

  It is attracted more strongly by one atom
• What does the unequal sharing of the electron pair cause?

  A buildup of a partial charge on one atom
• How is a partial charge represented in chemistry?

  As δ±
• What is the term for the ability of an atom to attract the electron pair?

  Electronegativity
• What scale is used to measure electronegativity?

  The Pauling scale
• Who invented the Pauling scale?

  Linus Pauling
• What charge does the most electronegative atom in a bond develop?

  A partial negative charge (δ-)
• What is the charge difference in a polar bond called?

  A permanent dipole
• Which bond is a good example of a non-polar bond?

  The C-H bond
• Why is the C-H bond considered non-polar?

  Electronegativities of hydrogen and carbon are similar
• Can molecules have an overall dipole like bonds?

  Yes, molecules can also be polar
• What is required for a molecule to be polar?

  It must have polar bonds
• What happens if there is charge separation in a molecule?

  There will be a permanent dipole
• Which molecule is an example of a polar molecule?

  Chloroform, CHCl3
• Is a molecule with polar bonds necessarily polar?

  No, it can be non-polar if symmetrical
• What happens to partial charges in a symmetrical molecule?

  They will be the same on each side
• What is electronegativity?

  Measure of attraction for shared electrons
• How is electronegativity measured?

  Using the Pauling scale
• Who invented the Pauling scale?

  Linus Pauling
• What is the trend of electronegativity across a period?

  It increases across a period
• Why does electronegativity increase across a period?

  Charge on the nucleus increases
• What happens to electronegativity as you move up a group?

  It increases up a group
• Why does electronegativity increase up a group?

  Bonding electrons are further from the nucleus
• What are polar bonds?

  Bonds where one atom is more electronegative
• What is a dipole?

  A small charge difference between atoms
• What is a permanent dipole?

  A constant charge difference in polar bonds
• What characterizes nonpolar bonds?

  Identical atoms with equal electronegativity
• What happens in a polar bond?

  Electrons are shared unequally
• How does electron density relate to electronegativity?

  Higher electronegativity means greater electron density
• What is the spectrum of bonds?

  Bonds range from ionic to covalent
• What defines a polar molecule?

  Overall dipole exists across the molecule
• What is an example of a polar molecule?

  Water (H2O)
• What is an example of a nonpolar molecule?

  Carbon dioxide (CO2)
• How does molecular symmetry affect polarity?

  Symmetry can cancel out dipoles
• What is the shape of water?

  Non-linear with a bond angle of 104.5 degrees
• Why is carbon dioxide nonpolar despite having polar bonds?

  It has a symmetrical linear shape
• What is the shape of dichloromethane (CH2Cl2)?

  Tetrahedral
• Why is dichloromethane a polar molecule?

  It is not symmetrical, dipoles don't cancel
• What is the definition of electronegativity?

  Ability of an atom to attract electrons