In the Goldschmidt correction, relative factors used to adjust this quantity are based on 12-fold coordinated close-packed structures. A different quantity named for Allred and Rochow (-5[1])equals 3590 times Z-effective over this quantity squared. (-5[1])The (-5[2])Hume-Rothery rules state a substitutional alloy will only form if this quantity for two elements is within 15% (15[1])of each (15[3])other. A (15[1])“hard sphere” model can be used to calculate the (*) van der Waals form of this (10[1])quantity. (10[1])Poor (10[1])shielding against nuclear charge by 4f electrons explains why this (10[1])quantity (-5[1])“contracts” for (10[5]-5[1])lanthanides. Like metallic (10[1])character, (10[1])this quantity decreases from left to (10[1])right across a (10[1]-5[1])period and increases down a group. For 10 points, an (10[1])atom’s size is (10[1])measured by what distance between an atom’s (10[1])nucleus (10[1])and outermost (10[1])electron? (10[1])■END■