He predicted an element with an atomic weight between 65 (zinc) and 75 (arsenic) with a valence similar to aluminum that he named ekaboron. This element was discovered in 1879. What is this element:?

Scandium

Explanation:

Mendeleev played an important role in the development of the modern periodic table. His periodic table was filled with gaps. He said that these gaps were elements that were yet to be discovered. He rightly predicted many elements which have now been discovered and fitted in their proper places in the periodic table.

He used the prefix ''eka'' to refer to elements whose properties were alike but were yet to be discovered at that time.

The compound named ekaboron which he predicted to have an atomic weight between 65 (zinc) and 75 (arsenic) with a valence similar to aluminum was later discovered in 1879 and properly named scandium.

if you're asking what comes out, it's steam.