12/15/08

Post date: Dec 15, 2008 2:18:58 AM

Bell Activity: Why do people form connections with other people?

    • Why chemical bonds form

      • Each atom wants to have a stable number of electrons

    • More atom anatomy

      • Charges

        • Atoms are made of protons, neutrons, and electrons

        • Protons have positive charge, electrons have a negative charge, neutrons have no charge

        • When not bonded, atoms have the same number of protons and neutrons, so net charge is 0

      • Electrons

        • Arranged in different levels or orbitals, with each level being able to hold a certain number of electrons

        • Valance electrons - the electrons in the outer-most level, involved in chemical bonding

          • Periodic table shows us how many valence electrons different atoms have by which column the element is in

        • Atoms want to have their outermost electron level filled up completely, and can do this in 2 ways

          • Take more electrons from another atom or give up electrons to another atom

            • When an atom gains electrons or gives them up, it is called an ion

          • Share electrons with another atom

          • These two methods result in 2 different types of bonds

        • Ionic bonds

          • Formed when one atom gives electrons to another

          • One atom is looking to get rid of electrons, another wants to get more, so electrons are transferred

          • The atom that gave up electrons has lost negative charge, and now has a positive charge. The atom that got more electrons has gained negative charge, and now has a negative charge. Since opposite charges attract, the positive ion is attracted to the negative ion.

          • Example: sodium bonding with chlorine

            • Sodium has 11 total electrons (atomic number is 11) and 1 of those is a valence electron (sodium is in the first column of the periodic table)

            • Chlorine has 17 total electrons (atomic number is 17) and 7 of those are valence electrons (7th column)

            • Sodium wants to get rid of one electron (so it has 8 valence electrons) and Chlorine wants to get one more electron (so it has 8 valence electrons)

            • Sodium gives one electron to Chlorine

            • Sodium (who lost one negative charge) now has a charge of +1 while Chlorine (who gained one negative charge) now has a charge of -1. The opposite charge attract each other, and the Sodium and Chlorine are pulled together.

      • Ionic analogy

          • In groups of 2 or 3, create an analogy for ionic bonds.

          • Write at least one paragraph explaining the analogy.

          • Present to the class tomorrow (Tuesday)

          • Example: My dog has 4 puppies, but I can only keep 2 of them. I give the other two to you, because you don't have any puppies and want 2. I then make it a point to keep in contact with you so that I can visit the other puppies, and we are thus "bonded" together.