Question

dmitri mendeleev created an early version of the periodic table based on atomic mass. the modern periodic table has elements placed because of-
atomic number.
electron properties.
atomic size.
the date the element was discovered.
question 3
dmitri mendeleev and lothar meyer created similar elemental tables in 1869. why was mendeleevs table \more valuable\ to modern science than meyers

Explanation:

The modern periodic table arranges elements by atomic number. Atomic number is the number of protons in an atom's nucleus and is a fundamental property for organizing elements. Electron properties, atomic size, and discovery date are not the primary basis for the modern periodic table's structure.

Answer:

atomic number.