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Textbook Analysis - Anthony Thomas
Part 1: Material Description
Title: Merrill Chemistry
Date of Publication: 1998
Authors: R. C. Smoot, R. G. Smith and J. Price
Grade: 11, 12
Ability Levels: all
Part 2: Unpacking of a Learning Goal
Atomic Structure. I focused on C4.8D Ions - ions can be formed through either the addition or loss of electrons. Ions are classified as either anions or cations. Anions have more electrons than protons in the atom, thus having a negative charge. Cations have more protons than electrons in the atom, thus having a positive charge.
Part 3: Analysis
Criterion III.A: Providing a Variety of Phenomena
0. Phenomena are useful in making the key ideas real.
0. Phenomena are explicitly linked to the relevant key idea
The textbook offers very few phenomena dealing with ions and atomic structure.
First, in chapter 7 there is a diagram, which shows how a box for sulfur in the periodic table shows what ionic charge the ion is likely to form. On the following page this is a discussion of polyatomic ions and a representation of hydroxide, sulfate and oxalate ions.
Three chapters later, in chapter 10, there is a section of the radii of atoms, followed by a discussion on the radii of ions. There is a periodic table, which shows the comparative size of the atoms versus that of the ions for all of the elements. In a separate figure they show the radii of both atomic sodium and atomic chloride and what happens to their sizes, as they become ions. With the diagrams of ion size they show how the orbitals of sodium and chloride atoms and ions and how the ions are the same as noble gases.
In both chapters there is a discussion about the connection between ionic charge and oxidation number. In chapter 10 there is again a chart showing an abbreviated periodic table and how each row is related to oxidation number though without explaining why elements in some rows may have more than one oxidation number.
In chapter 10, figure 10.8 there is a graph of atomic number versus ionization energy. They note that ionization energy is a periodic property and the values increases with each row or period. This is displayed again in a crude picture of the periodic chart showing increases in ionization energy as one moves up and to the right.
Overall, I would give this textbook a poor rating for this criterion. The central problem is that all discussions of ions are greatly separated from a discussion of atomic structure. In deed, in the section on atomic structure it is stated, “because an atom is electrically neutral, the number of electrons must equal the number of protons”. There is no mention of what happens when the number of protons and electron differ. As a consequence on how the book is organized the phenomena described are meant to address topic of “Symbols and Formulas” in chapter 7 and patterns built into the periodic table in chapter 10, Periodic Trends”.
Criterion III.B: Providing Vivid Experiences
Indicators: A: Each firsthand experience is efficient (when compared to other firsthand experiences) and, if several firsthand experiences target the same idea, the set of firsthand experiences is efficient. (The efficiency of an experience equals the cost of the experience [in time and money] in relation to its value.)
Indicator B: The experiences that are not firsthand (e.g., text, pictures, video) provide students with a vicarious sense of the phenomena. (Please note that if the material provides only firsthand experiences, this indicator is not applicable.)
Indicator C: The set of firsthand and vicarious experiences is sufficient.
The textbook offers a section they call the one minute experiment. In an experiement in chapter 7, the student measures out a set amount of sulfur and iron, mixes them and adds them to a test tube. The test tube is heated to red hot with a bunsen burner in a fume hood and then plunge into cold water, breaking the test tube. The product is then collected from water by forceps and the product examine. They suggest examining the difference between the starting materials and the product (smell, physical properties, magnetic properties).
Part 4 - Modifications -
This textbook does a very poor job of introducing the concept of ions. The logical spot to begin a discussion of ions in the atomic structure section. While the points in the text where they discuss ions are appropriate for the issue they are interested in, they start the discussion without an introduction of the topic. The concept of ions must be discussed in sections on bonding, chemical reactions, the periodic table and trends solutions, etc. Remarkably, there is no discussion of the terms cations and anions until a chapter on electrochemistry on page 655. It is unlikely that using this textbook, students would ever get to these fundamental terms. As mentioned earlier, this textbook offers very few phenomena dealing with ions and atomic structure, this has to be changed.
Another thing that is missing from this textbook is while there is a natural transition from a discussion of ions to a discussion of orbitals and the drive to fill orbital shells; this discussion is missing in this textbook. In the section on the filling orbitals in Chapter 5 there is no discussion of ions and why various elements form ions of different charges. In this subject alone this textbook will have to be substantially supplemented.
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