9/20/10

Post date: Sep 20, 2010 4:33:12 PM

Bell Ringer: Why do atoms form connections with each other?

    • Quiz 4 - Elements

    • Return assignments, mid-term grades

    • 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.

    • Sometimes atoms don't bond in equal numbers

      • Example: Magnesium bonding with Fluorine

        • Magnesium is in the 2nd column, so it wants to get rid of 2 electrons

        • Fluorine is in the 7th column, so it wants to add 1 electron

        • One atom of Magnesium needs to bond with 2 Fluorines to get rid of both of its extra electrons

        • Formula: MgF2

  • Ionic Bonding Homework (due tomorrow)

    • For each of the following combinations, write the chemical formula for the compound they form. You may do this using diagrams or using just the valence numbers from the periodic table (crossing the charges) for each. You must have at least one problem done using diagrams and at least one using just the periodic table, the rest you may do using whichever method you prefer.

    1. Beryllium and Oxygen

    2. Potassium and Nitrogen

    3. Magnesium and Chlorine

    4. Calcium and Sulfur

    5. Magnesium and Nitrogen

      1. Calcium and phosphorus

      2. Hydrogen and Carbon

      3. Lithium and Fluorine

      4. Beryllium and Nitrogen

      5. Magnesium and Silicon