Bond strength and polarity

• What does bond polarity deal with?

  Separation of charge within a covalent bond, creating a dipole
• What is electronegativity?

  A measure of the electron-attracting ability of an element when covalently bonded
• Why do atoms have different powers to attract electrons?

  Due to their size (radius) and nuclear charges
• How does the size of an atom affect its electronegativity?

  Smaller atoms can attract electrons more effectively due to closer proximity to the nucleus
• What is the electronegativity value of fluorine?

  1. 0
• What is the electronegativity value of carbon?

  1. 5
• What are the electronegativity values of the non-metals listed?

  • C: 2.6
  • N: 3.0
  • O: 3.5
  • F: 4.0
  • Si: 1.8
  • P: 2.1
  • S: 2.5
  • Cl: 3.0
  • Se: 2.4
  • Br: 2.8
  • I: 2.5
• What does the term 'induction' refer to in the context of charge?

  Attraction and movement of electrons
• How does electronegativity affect the charge of atoms in a bond?

  Higher electronegativity leads to a partial negative charge on that atom
• What symbol represents partial charges?

  The Greek letter small delta (δ)
• How does the water molecule demonstrate bond polarity?

  • Oxygen is more electronegative than hydrogen
  • Electrons are drawn towards oxygen
  • Results in a partial negative charge on oxygen
  • Results in partial positive charges on hydrogen atoms
• What is bond polarity?

  Separation of charge due to differences in electronegativity between bonded atoms
• When can a bond be considered non-polar?

  When the bonded atoms have similar electronegativity
• What are the electronegativity values of carbon and hydrogen?

  Carbon = 2.5 and Hydrogen = 2.1
• What is the charge separation in a dipole?

  A dipole has both direction and magnitude due to charge separation
• What is the relationship between dipoles and bond polarity?

  A bond with charge separation is called a dipole
• What are the characteristics of dipoles?

  • Dipoles are vector quantities
  • They have both direction and magnitude
  • They result from charge separation in bonds
• What are vectors?

  Vectors are quantities that have both magnitude and direction.
• How do vectors behave when added or canceled out?

  Vectors can add up or cancel out depending on orientation.
• What are dipoles in relation to vectors?

  Dipoles are vector quantities.
• What is the resolution of dipoles in molecules?

  • Dipoles can be resolved, added, and canceled out.
  • If dipoles do not cancel out, the molecule is polar.
  • Polar molecules have regions of positive and negative charge.
• What happens to the dipoles in a molecule if they cancel out?

  The molecule is non-polar.
• What is an example of a non-polar molecule?

  Carbon dioxide (CO2) is a non-polar molecule.
• Why is the carbon-oxygen bond in CO2 polarized?

  It is polarized due to the difference in electronegativity between carbon and oxygen.
• What are the electronegativities of carbon and oxygen?

  Carbon is 2.5 and oxygen is 3.5.
• How do the dipoles in CO2 behave?

  Both dipoles cancel out, leaving CO2 non-polar.
• Is water a polar or non-polar molecule?

  Water is a polar molecule.
• Why do the dipoles in water not cancel out?

  They do not cancel out due to the shape of the water molecule.
• How do the O-H bonds in water behave?

  The O-H bonds are equally polar but do not cancel out.
• How can the dipoles in a water molecule be resolved?

  • The dipoles can be resolved into horizontal and vertical components.
  • Horizontal components cancel out.
  • Vertical components add up, making the molecule polar.
• What is the overall dipole direction in a water molecule?

  The overall dipole is vertical, negative at the top and positive at the bottom.
• How can the polarity of a molecule be determined?

  1. Consider the relative electronegativities of the component atoms.
  2. Identify polarized bonds (dipoles).
  3. Inspect the molecule to see if individual dipoles cancel out.
  4. Symmetry of the molecule is important.
• How do dipoles behave in linear, trigonal planar, and tetrahedral molecules?

  1. Linear: Dipoles cancel if components are identical and oppositely arranged (e.g., BeCl2, CO2).
  2. Trigonal planar: Dipoles cancel if all three atoms bonded to the central atom are the same (e.g., BF3).
  3. Tetrahedral: Dipoles cancel if all four attached atoms are the same (e.g., CCl4).
• What is a consequence of polarity in molecules?

  Polar molecules are more attracted to one another and behave like tiny magnets.
• How can the polarity of liquids be demonstrated?

  By using a charged electrostatic rod to bend a stream of liquid from a burette.
• What does 'intermolecular' mean?

  Intermolecular refers to forces between one molecule and another.
• What happens when intermolecular forces are overcome?

  Molecules separate from one another, such as when a liquid boils.
• What are intramolecular forces?

  Intramolecular forces hold the molecule itself together, typically chemical bonds.
• What is an example of intramolecular forces?

  Hydrogen bonding from one part of a molecule to another part of the same molecule.