Because those elements were not discovered at the time Mendeleev proposed the Periodic Table.
The gaps in his table predicted the characteristics of elements that had not yet been discovered, and when they were, they matched his predictions
Mendeleev left some gaps in his table for the elements which were not discovered at that time.Those elements were later found as silicon,gallium,germanium which were then filled in the gaps
Ekasilicon is germanium['eka' is Sanskrit language for: 'first' place down under Si)Germanium was isolated in 1886, and provided the best confirmed prediction of Mendeleev's periodic table, which was built up before the discovery of Ge.(Professor Dmitri Mendeleev published the first Periodic Table of the Atomic Elements in 1869).When he proposed his periodic table, he noted some gaps in the table, and predicted that as-of-yet unknown elements existed with properties appropriate to fill those gaps.
He made the periodic table. When he found gaps he said there were unknown elements, he was right and those elements were found in his lifetime.Mendeleev was the first person to organize the elements into what we would recognize as a version of the modern periodic table.
no because if you look back in time more they didn't know as much as we do now so we learn more over time so if you looked back in time you wold see that there would be gaps in random spots on the periodic table. :)
he knew that because of the new elements that were formed and he figured that the atoms would pop back and forth and leave gaps in between them.
The gaps represented the elements which were not discovered. When the elements were invented, they were placed into these gaps.
Scientists suggest Mendeleev left gaps in the periodic table because Mendeleev knew the elements existed; however, was unable to prove it.
Those gaps were later filled by elements discovered after the creation of the table, which justified the gaps being left for that purpose.
There were gaps in the periodic table a hundred years ago because investigators had not discovered some elements yet, though there was a "place" for them in the array. Recall that through the genius of Mendeleyev, the elements had been given an "order" owing to their chemical properties. By creating a "chart" (the first periodic table), Mendeleyev could see where elements "would be" though none had yet been discovered. He could predict that eventually an element would appear "here" on the table and would have a "these" properties because of the arrangements in the array or table of element.
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.
Gaps
he knew that later on the gaps would eventually get filled up
The gaps estimated their chemical properties.The elements when discovered were found to have those properties.They were then placed in these gaps.
The gaps in his table predicted the characteristics of elements that had not yet been discovered, and when they were, they matched his predictions
It was recognized by the inventor of the Periodic table that these empty spaces are for elements/isotopes that would be discovered someday. Dmitri Mendeleev is generally credited with the publication, in 1869, of the first widely recognized periodic table. He developed his table to illustrate periodic trends in the properties of the then-known elements. Mendeleev also predicted some properties of then-unknown elements that would be expected to fill gaps in this table.
Because at that time there were no known elements to fill those gaps. The fact that they were filled indicated the power of his classification method. When a scientific theory predicts things clearly and these are later found, the theory becomes validated.