Question

Dmitri Mendeleev and Henry Moseley developed their periodic tables about forty years apart. During that time, many discoveries in chemistry were made. Which fact was most likely discovered between the time of Mendeleev’s table and the time of Moseley’s table that helped Moseley develop his version?

Answer 1

Answer:

Dmitri Mendeleev and Henry Moseley developed their periodic tables about forty years apart. During that time, many discoveries in chemistry were made.

Which fact was most likely discovered between the time of Mendeleev's table and the time of Moseley's table that helped Moseley develop his version?

The number of protons in an atom is different than the atom's total mass.