2/8/10

Post date: Feb 08, 2010 1:22:48 PM

Bell Ringer: How are molecules different from atoms?

    • Notes - chapter 6, section 1

      • Chemical bonds

        • The forces that hold atoms or ions together in a compound

        • Are a way to store energy

        • Can be broken and reformed to make new compounds

      • Chemical structure

              • Building Structure

              • The way a building's parts fit together

              • Can be represented with blueprints

              • Chemical Structure

              • The way the compound's atoms are bonded together to make the compound

              • Can be represented by various models

        • In pairs, come up with a way to "blueprint" a water molecule (1 oxygen atom and 2 hydrogen atoms)

          • Each pair draws theirs on the board

        • Other models commonly used

          • Ball and stick model

            • Atoms are represented by circles

            • Bonds are represented by sticks

            • Makes it easy to see shape of the compound

              • Bond angle - angle between bonds in a compound

              • Bond length - the distance between the nucleus of an atom and the nucleus of an atom it is bonded to

          • Structural formulas

            • Similar to ball and stick, but use the chemical symbols to represent the atoms

            • No bond angle or length recorded on drawing

            • Often show positions of electrons

          • Space-filling model

            • Shows the relative sizes of atoms in a compound, but not bond lengths

          • Each example shows a model of water (2 hydrogens and one oxygen) in a different way to present different information

        • Bonds can bend, stretch, and rotate without breaking.

          • Atoms are constantly in motion, vibrating and spinning around, but this does not break the bond

          • We usually show a bond with a solid line, but it really behaves more like a flexible spring

  • Draw a ball and stick model and space-filling model for each of the following compounds. For the space-filling model, assume that the larger atomic number an atom has, the more space it fills.

      • Oxygen gas, 02 (bond angle=180, length = 122pm)

    • Carbon dioxide, CO2 (bond angle=180, length =143pm)

    • Ammonia, NH3 (bond angle=109, length =101pm)

    • Dihydrogen sulfide, H2S (bond angle=92, length = 96pm)

      • Sulfur dioxide, SO2 (bond angle=120, length =151pm)