Question

there are 38 ____ metals in groups 3 through 12 of the periodic table.

Explanation:

In the periodic table, groups 3 through 12 contain transition metals. The number of transition metals (considering the d - block elements and including the f - block elements which are also part of the transition metals in a broader sense) totals 38. So the word to fill in the blank is "transition".

Answer:

transition