20. What prediction did Mendeleev make that came true less than 20 years later?
He said that the periodic table would be developed into 18 families.
He predicted the atomic numbers of unknown elements.
He said that three new elements would be discovered.
He predicted that a total of 112 elements would be discovered.

20. What prediction did Mendeleev make that came true less than 20 years

later?

He said that the periodic table would be developed into 18 families.

He predicted the atomic numbers of unknown elements.

He said that three new elements would be discovered.

He predicted that a total of 112 elements would be discovered.

i think its 100

i hope this !