[Curmudgeon]

Biochemistry is by its nature somewhat restrictive. The six major elements involved are carbon, hydrogen, nitrogen, oxygen, calcium and phosphorus. Because nitrogen and phosphorus belong to the same family in the periodic table, they react similarly to the same chemicals. Those five families that are represented cover a bit more than half of the periodic table and you can probably find some of the missing families among the roughly eighteen elements that have minor occurrences in biochemistry but even so, he has probably never dealt with the elements of the lathanide and actinide series in the table.