21. when dr. mendeleev created the first periodic table, what did he base it on? number of neutrons number…

21. when dr. mendeleev created the first periodic table, what did he base it on? number of neutrons number of electrons atomic number atomic mass

21. when dr. mendeleev created the first periodic table, what did he base it on? number of neutrons number of electrons atomic number atomic mass

Answer

Answer:

Atomic mass

Brief Explanations:

Mendeleev's first periodic - table was based on atomic mass. He arranged elements in order of increasing atomic mass and noticed periodic trends in their properties.