14. Consider the melting point data for the natural forms of the second row elements. Calculate Z* using Slater's rules for the outermost electron for each of these elements. Does Z* give a reasonable accounting of the trend in the melting point? Why or why not? Should melting point be considered a periodic property of atoms? Why or why not?
Melting Point (°C)
Na 98 Mg 650 Al 660 Si 1414 P 44 S 115 Cl –101.5 Ar –189
First, find the electron configuration to calculate Z*:
There is no correlation between the melting points and Z*. This is not surprising because Z* is associated with isolated atoms (i.e., gas phase), not the solid or liquid phases. The melting point of a substance is determined by intermolecular interactions between atoms or molecules in the condensed phases. Thus, melting point might be considered a periodic property, but requires an understanding of all of the bonding attractions in place for each substance.