Standard potential periodic variation

FIGURE 12.9 The variation of standard potentials through the main groups of the periodic table. Note that the most negative values are in the s block and that the most positive values are close to fluorine. 

In complex experimental programs, blocking may be done for potentially perturbing factors that cannot be controlled, such as ambient temperature or humidity variations, by conducting several evaluations of the response in short time periods, where temperature and humidity are relatively constant. Dividing the total experiment into these blocks, or relatively uniform groupings, improves the quality of the estimated effects by reducing the standard error of the measurements. 

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