12/11/08

Post date: Dec 10, 2008 12:2:22 AM

Bell Activity: What holds a compound together?

    • 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 Carbon dioxide molecule (1 carbon atom and 2 oxygen 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

        • 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, structural formula, 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

      • Carbon dioxide, CO2

      • Carbon monoxide, CO

      • Dihydrogen sulfide, H2S

      • Tin fluoride, SnF2

      • Sucrose, C6H12O6