Intermolecular Forces

• What is electronegativity?

  The tendency of an atom to attract electrons
• How is electronegativity measured?

  Using the Pauling scale
• What is the electronegativity of fluorine?

  3.98
• Who developed the Pauling scale?

  Linus Pauling
• What defines a nonpolar covalent bond?

  Electrons are shared equally between atoms
• When do nonpolar covalent bonds occur?

  When electronegativity difference is less than 0.4
• What creates a polar covalent bond?

  Unequal sharing of electrons between atoms
• What is the electronegativity difference range for polar covalent bonds?

  Between 0.4 and 1.7
• What charge does chlorine have in HCl?

  Partial negative charge (δ-)
• What is a permanent dipole?

  Areas of positive and negative charge that don't change
• What is required for a molecule to have a permanent dipole?

  Polar bonds and an asymmetric shape
• Why does carbon dioxide (CO₂) not have a permanent dipole?

  Its polar bonds are arranged symmetrically
• Why does ammonia (NH₃) have a permanent dipole?

  Its shape is pyramidal, aligning dipoles
• What are intermolecular forces?

  Forces of attraction or repulsion between molecules
• What do intermolecular forces affect?

  Physical properties like boiling and melting points
• What are Van der Waals forces?

  Weak attractions between all molecules
• What causes Van der Waals forces?

  Temporary fluctuations in electron distribution
• How do geckos use Van der Waals forces?

  To climb smooth surfaces with strong grip
• How do larger molecules affect Van der Waals forces?

  Larger molecules have stronger Van der Waals forces
• What is the relationship between surface area and Van der Waals forces?

  Larger surface areas lead to stronger forces
• What type of interactions occur between molecules with permanent dipoles?

  Dipole-dipole interactions
• What is hydrogen bonding?

  The strongest form of intermolecular bonding
• What is required for hydrogen bonding to occur?

  A hydrogen atom bonded to a highly electronegative atom
• Why is hydrogen bonding stronger than typical dipole-dipole interactions?

  Due to high charge density on hydrogen
• How does hydrogen bonding affect water's boiling point?

  It raises the boiling point significantly
• Why does ice float on water?

  Ice is less dense due to hydrogen bonds
• How do boiling points of Group 6 hydrides compare?

  Hydrogen bonding increases boiling points
• What happens to boiling points in Group 7 hydrides?

  They increase down the group due to induced dipoles
• What is the boiling point of hydrogen fluoride (HF)?

  Higher due to strong hydrogen bonds
• How do permanent dipole-dipole interactions behave in hydrogen chloride (HCl)?

  The positive end attracts the negative end of another dipole
• How do hydrogen bonds influence the properties of substances?

  They increase boiling and melting points significantly
• What is the effect of hydrogen bonding on the structure of ice?

  It forms a rigid lattice structure
• Why do larger halogen atoms lead to higher boiling points in Group 7 hydrides?

  They enhance induced dipole-dipole interactions
• How do the boiling points of Group 6 hydrides compare to those of Group 7 hydrides?

  Group 6 hydrides have higher boiling points