chem2

• What is the definition of ionic bonding?

  Ionic bonding is the electrostatic force of attraction between oppositely charged ions formed by electron transfer.
• How do metal and non-metal atoms behave in ionic bonding?

  Metal atoms lose electrons to form positive ions, while non-metal atoms gain electrons to form negative ions.
• Why does MgO have a higher melting point than NaCl?

  MgO has a higher melting point because the ions Mg$^{2+}$ and O$^{2-}$ are smaller and have higher charges than Na$^{+}$ and Cl$^{-}$.
• What is a giant ionic lattice?

  • A regular 3D arrangement of ions in an ionic solid.
  • Each ion is surrounded by oppositely charged ions.
  • Example: Na$^{+}$ ions are surrounded by six Cl$^{-}$ ions.
• What are the properties of ionic compounds when solid and molten?

  They are non-conductors of electricity when solid but good conductors when molten or in solution.
• What is the definition of covalent bonding?

  A covalent bond is the strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms.
• What is a dative covalent bond?

  A dative covalent bond forms when the shared pair of electrons in the covalent bond comes from only one of the bonding atoms.
• What is the shape of the NH$_{4}^{+}$ ion?


  The shape of NH$_{4}^{+}$ is tetrahedral.
• What are the differences between ionic and covalent bonding?

  • Ionic: Electrostatic attraction between oppositely charged ions.
  • Covalent: Sharing of a pair of electrons between atoms.
  • Ionic compounds have high melting points; covalent compounds have low melting points.
• What are typical examples of ionic compounds?

  Examples include sodium chloride and magnesium oxide.
• What are the properties of giant ionic compounds compared to simple molecular compounds?

  Giant ionic compounds have high melting points and are generally soluble in water, while simple molecular compounds have low melting points and are generally poor in solubility.
• What are the shapes and bond angles of common molecular geometries?

  • Linear: 180° (e.g., CO$_{2}$)
  • Trigonal planar: 120° (e.g., BF$_{3}$)
  • Tetrahedral: 109.5° (e.g., SiCl$_{4}$)
  • Trigonal pyramidal: 107° (e.g., NCl$_{3}$)
  • Bent: 104.5° (e.g., H$_{2}S$)
  • Octahedral: 90° (e.g., SF$_{6}$)
• How do lone pairs affect bond angles?

  Lone pairs repel more than bonding pairs, reducing bond angles by about 2.5° per lone pair.
• What is electronegativity and how does it vary in the periodic table?

  • Electronegativity is the tendency of an atom to attract electrons in a covalent bond.
  • It increases across a period and decreases down a group.
• What is a polar covalent bond?

  A polar covalent bond forms when the elements in the bond have different electronegativities, leading to an unequal distribution of electrons.
• How does a symmetric molecule affect its polarity?

  A symmetric molecule will not be polar even if individual bonds are polar, as the dipoles cancel out.
• What are the types of intermolecular forces?

  • Induced dipole-dipole interactions (London forces)
  • Permanent dipole-dipole forces
  • Hydrogen bonding
• What are induced dipole-dipole interactions?

  Induced dipole-dipole interactions occur between all simple covalent molecules and noble gases due to fluctuating electron density.
• What factors affect the strength of induced dipole-dipole interactions?

  The more electrons there are in the molecule, the stronger the induced dipole-dipole interactions will be.
• What are permanent dipole-dipole forces?

  Permanent dipole-dipole forces occur between polar molecules and are stronger than induced dipole-dipole interactions.
• How do boiling points vary among different types of intermolecular forces?

  • Hydrogen bonding leads to higher boiling points.
  • Permanent dipole-dipole interactions lead to moderate boiling points.
  • Induced dipole-dipole interactions lead to lower boiling points.
• What is hydrogen bonding and when does it occur?

  Hydrogen bonding occurs in compounds with hydrogen attached to nitrogen, oxygen, or fluorine, which must have an available lone pair of electrons.
• Why does water have a high boiling point compared to other similar molecules?

  Water has a high boiling point due to hydrogen bonding between its molecules.

  
• What is the structure of ice compared to liquid water?

  • Ice has a regular arrangement of molecules held apart by hydrogen bonds.
  • This structure explains the lower density of ice compared to liquid water.
• What type of interactions hold iodine molecules together in solid iodine?

  Weak induced dipole-dipole interactions hold iodine molecules together in solid iodine.
• What is the role of lone pairs in hydrogen bonding?

  Lone pairs on electronegative atoms are necessary for hydrogen bonding to occur.
• How does the shape of a molecule affect induced dipole-dipole interactions?

  Long chain alkanes have a larger surface area for induced dipole-dipole interactions compared to spherical shaped branched alkanes.
• What are van der Waals' forces?

  • Van der Waals' forces include both permanent dipole-dipole and induced dipole-dipole interactions.
  • They are weaker than hydrogen bonds.
• What is the significance of hydrogen bonding in water?

  Hydrogen bonding in water leads to its anomalously high boiling point and unique properties like lower density in ice.
• What types of compounds can form hydrogen bonds?

  Alcohols, carboxylic acids, proteins, and amides can all form hydrogen bonds.
• How does the molecular structure of ice differ from that of liquid water?

  In ice, molecules are held further apart than in liquid water due to hydrogen bonding, resulting in lower density.
• What are the trends of electronegativity in the periodic table?


  • Increases from left to right across a period
  • Decreases down a group