Mendeleev left those gaps for the elements which were not discovered at that time. He named those elements like eka-aluminium,eka -silicon etc.
Mendeleev was able to predict the properties of the elements that were not discovered at that time. He left gaps for these elements in his Periodic Table.
Gaps
Because those elements were not discovered at the time Mendeleev proposed the periodic table.
Scientists suggest Mendeleev left gaps in the periodic table because Mendeleev knew the elements existed; however, was unable to prove it.
Dmitri Mendeleev is generally credited, as he was able to predict the properties of elements which had not yet been discovered based on 'gaps' in his table. He ordered the known elements in terms of their atomic mass in 1869; elements are listed in order of increasing atomic number in the modern version.
he knew that later on the gaps would eventually get filled up
He is credited as being the creator of the first version of the periodic table of elements. Using the table, he predicted the properties of elements yet to be discovered.
In 1869, he published the greatest of his works, Principles of Chemistry, where he formulated his famous periodic table, translated into many languages ​​and that was a textbook for many years.
A variety of people are claimed to have helped create the periodic table including Kekule and John Newlands, but the credit to how the Periodic Table currently looks (some gaps filled in by other chemists) typically goes to Mendeleev.
Mendeleev was the inventor of the Periodic Table. He organized all the known elements into the periodic table based on atomic number. He was also able to predict the existence of elements that had not yet been discovered based on gaps in the table he created. Based on observations of other elements in the groups he was also able to predict the characteristics of these unknown elements as well. NICE! dude
When Mendeleev proposed his periodic table, he noted gaps in the table, and ... Initial versions of the periodic table did not give the rare earth elements the ... that these atomic elements would be discovered, that he included them in later.
The gaps in his table predicted the characteristics of elements that had not yet been discovered, and when they were, they matched his predictions