Question

drag the missing word into place
so, dmitri mendeleev lined us elements up,
he was able to put us in the
we go in order of the number of protons we have
options: periodic table, matter, molecule

Explanation:

Dmitri Mendeleev is known for creating the periodic table of elements, where elements are arranged by the number of protons (atomic number). "Matter" is a general term for substances, and "molecule" is a group of atoms, so neither fits here. The correct word is "periodic table" as it relates to how Mendeleev organized elements.

Answer:

periodic table