Investigating Reduction Potential and Electronegativity for Elements

There is a relationship between reduction potential and electronegativity for an element. Using the graphing calculator, you can estimate unknown reduction potentials.

Adjust the window on your calculator to the following settings.

Table 1 Xmin = -4 Xmax = 4 Element Red Pot Electronegativity Xscl 1 Ymin = 0 Li -3.05 1.0 Ymax = 5 Rb -2.98 0.8 Yscl = 1 K -2.93 0.8 •Ba -2.90 0.9 1. Enter the reduction potential and •Ca -2.87 1.0 electronegativity data in table 1 into the Na -2.71 0.9 calculator lists. •Mg -2.37 1.2 Al -1.66 1.5 2. Construct a scatter plot of electronegativity vs. reduction potential. •Mn -1.19 1.5 •Zn -0.76 1.6 3. Determine straight line equation that relates Cr -0.74 1.8 reduction potential to electronegativity and Fe -0.44 1.8 add this function to the scatter plot. •Ni -0.25 1.8 •Sn -0.14 1.8 4. Use the trace features of the calculator to •Pb -0.13 1.8 estimate the reduction potentials of the •Cu +0.34 1.9 following elements: ••I +0.54 2.5 Hg +0.79 1.9 a. cadmium electronegativity = 1.7 Ag +0.80 1.9 b. cobalt electronegativity = 1.8 ••Br +1.07 2.8 c. strontium electronegativity = 1.0 •Pt +1.20 2.2 ••Cl +1.36 3.0 Au +1.50 1.9 ••F +2.87 4.0 Predict changes in the graph if the data for the halogens is removed. (Halogens are marked by a bullet).

Predict changes in the graph if only data for the divalent metal atoms is plotted.

Table Two Use your graphing calculator and the data atomic reduction covalent in table two to construct the following two number potential radius graphs. (Be sure to clear out all of the data 3 -3.09 1.52 and calculations from the previous activity, 4 -1.85 1.0 including lists, equations and plots). 9 2.87 0.30 11 -2.71 0.95 1. Reduction potential vs. atomic number 12 -2.37 1.6 2. Covalent radius vs. the atomic number. 13 -1.66 1.43 16 -0.48 1.04 17 1.36 0.99 Suggestions for graphing: 19 -2.93 1.33 20 -2.87 1.97 a. Create two connected line plots, one for 21 -2.08 1.6 each set of data. Use different plot 22 -1.63 1.46 markers for each data set. 23 -1.18 1.31 24 -0.91 1.25 b. When entering negative numbers be 25 -1.18 1.29 sure to press the (-) key and not the 26 -0.44 1.26 subtraction key. 27 -0.28 1.26 28 -0.25 1.24 29 0.34 1.28 30 -0.76 1.33 31 -0.53 1.22 34 -0.40 1.17 35 1.07 1.14 37 -2.93 1.48 38 -2.89 2.15 39 -2.37 1.8 40 -1.53 1.57 46 0.99 1.38 47 0.80 1.44 48 -0.40 1.49 49 -0.34 1.62 53 0.54 1.33 55 -3.02 2.62 56 -2.90 2.17 57 -2.52 1.88 After constructing the graphs, make sure both are visible and adjust the window to include both plots.

Inspect the two plots. a. Trace the plots and list the atomic numbers of the elements having "peak" reduction potentials. b. Create another list of elements having low point or "valley" reduction potentials. c. Explain why atomic numbers 30 and 48 have lowered reduction potentials. d. By simple inspection, does there appear to be any relationship between the "peaks" of the reduction potential and the "valleys" of the covalent radius plot?

Use the trace function of the calculator to determine values, construct a table with the following headings and add data for the "peaks" and "valley" elements on your graphs.

Atomic Number Reduction potential Electronegativity

Continue until you have covered all the "peaks" and valleys" of the reduction potential plot along with the corresponding covalent radii of the same elements (atomic numbers).

Use this data set to try determine if there is a plausible mathematical function between the covalent radius and reduction potential "peaks and valleys."

Some of this idea comes from Holt Chemistry Visualizing Matter p.608 The data below is a taken from the previous exercise. Y = -.295X + 1.43 R = 0.935 A B C 1 atomic number reduction potential covalent radius 2 9 2.87 0.64 3 11 -2.71 1.86 4 17 1.36 0.99 5 19 -2.39 2.31 6 29 0.34 1.28 7 30 -0.76 1.33 8 35 1.07 1.14 9 37 -2.93 2.44 10 46 0.99 1.38 11 48 -0.4 1.49 12 53 0.54 1.33 13 55 -3.02 2.62