Ionic bonds have chemical and physical properties that are typically different from covalent compounds. Crystal formation is almost exclusively due to ionic compounds.
Standard 1- Basic operations and concepts
Standard 2- Social, ethical, and human issues
Standard 3- Technology productivity tools
Standard 4- Technology communications tools
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Standard 1- The student accesses information efficiently and effectively
Standard 2- The student evaluates information critically and competently
Standard 3- The student uses information accurately and creatively
Reside at the heart of the discipline
Interactions of Matter
Represents a big idea having enduring value beyond the classroom:
Crystals have similar properties.
Require uncoverage, meaning that misconceptions need to be identified and clarified:
Ionic bonds are energetic interactions not physical connections. Ionic compounds do not exist as molecules but as ions in crystal lattices. The ion ratios in the crystal lattice is the compound's formula.
Offer potential for engaging students:
Students will construct a crystal of gumdrops and tooth picks. Students will also form crystals in a laboratory experience.
Exit cards, journal responses, and the construction of a 3-dimensional model will each be utilized in this unit. Exit cards will be used after the introduction of a new concept so that the instructor may evaluate the need for reteaching or redirecting the students. In journal responses the teacher should look for statements that would indicate an incorrect understanding or misconception. The students will have completed a brief research project and built a model of a particular crystal structure. The crystal model should represent a simple binary ionic crystal like NaCl, MgO, KCl, NaF...
Ask the students what are the differences is between salt and sugar. List responses then categorize by physical and chemical properties. Move the discovery to the point that salt is made of ions and sugar is not.
With a set of red and white balls (or other colors) the students will be asked to lay out the colored balls so that balls of the same color are as far from each other as possible. Then have the students make an arrangement that is 3-dimensional and still keep the colors separated. Ask the students how they suppose that negative ions and positive ions will arrange with each other.
Ask the students to complete these phrases; "Opposite charges _________" and "Like charges __________". The opposite charges (colors) were attracted to each other and the similar charges (colors) were repelling each other. Begin notes on ionic bonds and crystal structures while incorporating models of the crystal structures.
Given a particular compound or element the students are to research its crystal structure and build a model from gumdrops and toothpicks then present the model to the class. Real life examples are encouraged. X-ray crystallography could easily be incorporated here as an extension.
Exit cards will be used to indicate areas that need reteaching or clarification. There will be a short quiz to check for the students ability to identify ionic bonded compounds.
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