In this lesson, students will be introduced to the basic relationship between atomic structure and chemical bonding. This introduction will focus on ionic and covalent bonds. The lesson will connect trends in bonding behavior to the locations of elements on the periodic table. When the lesson has been completed, students will be able to the bonding behavior of various groups of elements.
Type of Task:
This lesson builds on information on the characteristics and trends in the periodic table. Students should understand how to relate the position of an element to its atomic number and mass (CA standard 1a), they should be to be able to identify metals, semimetals, nonmetals, and halogens (1b), and they should be able to identify trends in atomic size and electronegativity (1c). The new information will focus on bonding, so students will know how to use the periodic table to determine the number of electrons available for bonding (1d). They will know that bonds are formed when electrons are shared or exchanged (2a), and they will understand how electronegativity and ionization energy relate to bond formation. Students will know salt crystals, such as NaCl, are repeating patterns of positive and negative ions held together by electrostatic attraction(2c). Students will also be introduced to Lewis Dot Structures (2e).
Students should have had some introduction to atomic structure and the periodic table. The lesson focuses on how characteristics of different groups of elements influence bonding, and how positions on the periodic table can be used to predict bonding behavior.
Students will define ionic and covalent bonds, and they will explain in simple terms (e.g., using Lewis dot structures) the bonding behavior of nonmetals, the alkalis, and the alkaline earth elements.
Materials: Whiteboard and dry erase markers; computer projector; 5 slides; molecular building blocks (marshmallows, gummi candies, toothpicks)
Text of Learning Exercise:
A. Periodic table
1. review trends in periodic table
a. electronegativity, ionization energy, valence electrons, atomic size
2. talk about stable configurations
3. properties of particular groups
B. Types of chemical bonds
C. Lewis Dot structures
1. duet rule and octet rule
(1) 1. Begin by showing a cartoon with scientists.
(2) 2. Put up Slide 1 (Objective)-A student will paraphrase the objective
(3) 3. Distribute candy atomic and molecular components.
(3) 4. Put up Slide 2-show trends in periodic table
(5) 5. Put up Slide 3-talk about stable electron configurations; have students build candy atoms with filled and unfilled electron shells
(1) 6. Put up Slides 4 and 5-discuss animations/diagrams of ionic and covalent bonding
(10) 7. Using slides and diagrams, show students how to make physical models of simple molecules. Focus on NaCl, H2, and CH4. Relate these structures to Lewis Dot Structures.
(1) 8. Close by summarizing the bonding types and talking how they fit with trends in periodic table. Say that we will build on this in the next lecture with more complicated structures.
(2) 9. Evaluate by asking different students to predict the behavior and molecular formulas of metals and nonmetals we have not talked about.