Question

Name some of the elements that were discovered during Mendeleev time for which he had left the places of gaps

Answer 1

It was later identified as gallium. Gallium, germanium, and scandium were all unknown in 1871, but Mendeleev left spaces for each and predicted their atomic masses and other chemical properties

Answer 2

ecaboron, ecaalumaniun, etc

are the elements but later named as germanium, scandium, etc

also some nobal gasses were discovered such as Argon due to which he created zero group.

hope it helps...