chem

• Avogadro


  An Italian scientist who studied the behavior of gases
• Avogadro studied the behavior of gases

  1811
• Loschmidt


  Estimated the average diameter of the molecules in air and was able to calculate the number of particles in a given volume of gas
• Loschmidt estimated the average diameter of molecules in air


  1865
• Millikan


  Measured the charge on an electron. From the charge on a mole of electrons, he divided the two and obtained Avogadro's number
• Millikan measured the charge on an electron


  1910
• Perrin


  Earned the Nobel Prize for computing Avogadro's number using many different methods and named this constant in honor of Avogadro. Used oxygen as a standard and proposed "Avogadro's number is the number of molecules in exactly 32-grams of oxygen."
• Perrin earned the Nobel Prize for computing Avogadro's number


  1926
• The standard was later changed to the carbon-12 isotope
• Mole (mol)


  A unit in chemistry that serves as a bridge between the atomic and macroscopic worlds
• Ionic Compounds


  • Ionic bonds are very strong
  • Are solids at room temperature
  • Have high melting and boiling points
  • Made of a metal and a nonmetal
  • Does not conduct electricity in solid state, but does in the liquid and aqueous states
• Aqueous


  Dissolved in water
• Metals


  Lose electrons
• Nonmetals


  Gain electrons
• Chemical formula


  Arranged in the smallest whole number ratio (empirical formula)
• Formula unit


  The smallest repeating pattern within a crystal
• Even though ionic compounds are made up of ions, they are electrically neutral
• Covalent bonding


  A sharing of electrons
• Single covalent bond


  Made up of two electrons
• Covalent bond


  One electron is donated to the bond from each atom
• Molecules of the same compound are IDENTICAL and INDEPENDENT of each other
• Covalent bonding occurs between nonmetals only
• Atoms that are covalently bonded

  Called molecules or molecular compounds
• Covalent bonds


  • Much weaker than ionic bonds
  • Much lower melting and boiling points
  • Is a solid, liquid, or gas at room temperature
  • Non-conductors in any state
• Molecular formula


  The chemical formula for a covalently bonded group of atoms
• Molecular formula indicates the exact makeup of one molecule