6 - Shapes of Molecules and Intermolecular Forces

    Cards (49)

    • What does electron pair repulsion theory explain?
      Shapes of molecules and polyatomic ions
    • Why do electron pairs repel one another?
      They have a negative charge
    • What determines the shape of a molecule or ion?
      Electron pairs surrounding a central atom
    • How are electron pairs arranged in a molecule?
      As far apart as possible
    • What is the result of minimizing electron pair repulsion?
      Holds bonded atoms in a definite shape
    • What shape does methane (CH4) have?
      Tetrahedral shape
    • How many C-H covalent bonds does methane have?
      Four C-H covalent bonds
    • What is the bond angle in methane?
      109.5 degrees
    • How are 3D shapes represented in molecular diagrams?
      Using wedges and solid lines
    • What is a lone pair of electrons?
      Electrons that are not involved in bonding
    • How does a lone pair affect molecular shape?
      It repels more strongly than bonding pairs
    • What shape do CH4, NH3, and H2O have?
      Tetrahedral shape
    • How does the presence of lone pairs affect bonding angles?
      Decreases the bonding angle by 2.5 degrees
    • How are multiple bonds treated in electron pair repulsion theory?
      As a single bonding region
    • What shape does CO2 have?
      Linear shape
    • What happens to bond angles with more electron pairs?
      Bond angles decrease
    • What shape do three bonding pairs (e.g., BF3) have?
      Trigonal planar shape
    • What is the bond angle in an octahedral shape?
      90 degrees
    • What shape do six electron pairs give?
      Octahedral shape
    • How many bonded pairs does ammonia have?
      Four bonded pairs
    • What shape do carbonate and nitrate ions have?
      Trigonal planar shape
    • What is electronegativity?
      Attraction of an atom for shared electrons
    • What does the Pauling scale measure?
      Electronegativity values of elements
    • Which element is the most electronegative?
      Fluorine
    • What indicates an ionic bond based on electronegativity difference?
      Difference greater than 1.8
    • What characterizes non-polar bonds?
      Electrons shared equally between atoms
    • What is a dipole in a polar covalent bond?
      Separation of opposite charges
    • How do polar molecules behave with dipoles?
      Dipoles may reinforce or cancel each other
    • Why is water considered a polar molecule?
      It has two O-H bonds with dipoles
    • How does carbon dioxide behave as a molecule?
      It is nonpolar due to opposing dipoles
    • How does water dissolve sodium chloride?
      Water molecules attract Na+ and Cl- ions
    • What are intermolecular forces?
      Weak interactions between different molecules
    • What are the types of intermolecular forces?
      Induced dipole-dipole, permanent dipole-dipole, hydrogen bonding
    • What is the strength range of London forces?
      1-10 kJ/mol
    • What is the strength range of hydrogen bonds?
      10-40 kJ/mol
    • What happens to induced dipoles in London forces?
      They are temporary and constantly changing
    • How does the number of electrons affect London forces?
      More electrons increase induced dipole strength
    • What are simple molecular substances?
      Small units with a definite number of atoms
    • What state do simple molecular substances exist in?
      Solids, liquids, or gases at room temperature
    • Why do simple molecular substances have low melting and boiling points?
      Weak intermolecular forces require little energy
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