The elements in the groups 3-12 are transition elements
An element located in the middle of the periodic table would likely be classified as a transition metal. These elements typically have properties such as high melting and boiling points, variable oxidation states, and the ability to form colored compounds.
The bottom section of the periodic table is for the lanthanides and actinides, which are also known as the inner transition metals. These elements are placed below the main body of the periodic table to keep it compact, as they would otherwise disrupt the table's organization.
There are 117 elements on the periodic table, however, there is one blank spot that lies on the periodic table of elements, it has the atomic number of 117. If it were discovered, there would be 118 elements on the periodic table of elements.
If new elements are placed, then they would be appended in the periodic table. It won't disturb existing periodic table.
The largest category on the periodic table is the transition metals, which includes elements like iron, copper, and gold. These elements are known for their good conductivity, malleability, and ability to form colorful compounds. They are located in the middle of the periodic table between the main group metals and the nonmetals.
My answer for this would be Colour of the elements.
This is to my opinion not very probable, though never say impossible: Today Mendelejev's Periodic Table looks rather incomplete, there were no 'transition' elements in it (group 3 - 12)
NH3 is the chemical formula of the compound ammonia. The periodic table lists elements and not compounds.
Metallic elements make up about 70% of the Periodic Table of Elements.
Elements in the periodic table that are similar to sulfur would be oxygen, and selenium
Elements and atomic number
Mendeleev left blank spaces because certain elements on the Periodic Table were not known at that time. He knew that in the future, those elements would be found and placed on the periodic table.