Question

How did Dmitri Mendeleev deal with elements that had not yet been discovered?

He left blanks for them in his periodic table, as he predicted they would be discovered.

He created them in his laboratory and placed them in his table.

He ignored them, placing them in the table and shifting others when they were discovered.

He gave them names and properties and placed them in the table.

Answer 1

A. He left blanks for them in his periodic table, as he predicted they would be discovered.

Answer 2

he left blanks for them