Carbon in the form of diamond or nanotubes. Tin and Lead would be, but they are metals instead.
Silicon, which is just below carbon, and Germanium are the two elements that are most like carbon.
carbon, germanium, tin, lead
Yes; in his time not every element was known. As every element in the same column (group) has more or less the same chemical properties, he predicted there should be an element that was not yet discovered at some places. For example, under Silicon, there was a gap where he suspected that, to complete the pattern, a new element was missing; he called it eka-silicon, and correctly predicted many of its properties. The new element was found later, with properties very similar to the predictions; it was eventually called Germanium.
Gallium and arsenic because they are ekasilicon's closest neighbors, and would therefore have very similar properties
The holes suggested that there were "missing" elements that hadn't been discovered yet. Mendeleev successfully predicted the basic properties of germanium, which hadn't been discovered at the time, based on the properties he expected an element in that position to have. He called it "eka-silicon" (eka is a Sanskrit word meaning "one", because it was one period "higher" than silicon).When germanium was later discovered and turned out to have properties very similar to what Mendeleev had predicted, it went a long way towards validating Mendeleev's concept.
The element with chemical properties most like silicon is germanium. As an example, both are used in semiconductors.
carbon, silicon, germanium, tin, and lead.
Germanium
Silicon, which is just below carbon, and Germanium are the two elements that are most like carbon.
a metalloid in the carbon group and is chemically similar to silicon
In 1886 a German chemist named, Clemens A. Winkler discovered germanium. He discovered the first trace of germanium in the mineral argyrodite, while isolating it. (But germanium rarely makes distinct minerals.) He purified it to find the new element. Before this in 1871 a chemist named, Mendeleev predicted there would be a new element, that would have properties similar to the ones in silicon. His predictions were proved to be true.
Elements in Group 14 on the Periodic Table have similar properties to carbon. These elements are carbon (C), silicon (Si), germanium (Ge), tin (Sn), lead (Pb), and flerovium (Fl). Each of these elements has two electrons in the outermost p orbital, the electron configuration ns2np2, and they tend to adopt oxidation sates of +4 (+2 for the heavier elements due to the inert pair effect). Silicon is most similar to carbon.
I'm no expert, but both germanium and silicon are located in the same group on the periodic table. Elements in the same group are chemically similar because they contain the same number of valence electrons.
In 1886 a German chemist named, Clemens A. Winkler discovered germanium. He discovered the first trace of germanium in the mineral argyrodite, while isolating it. (But germanium rarely makes distinct minerals.) He purified it to find the new element. Before this in 1871 a chemist named, Mendeleev predicted there would be a new element, that would have properties similar to the ones in silicon. His predictions were proved to be true.
silicon
carbon, germanium, tin, lead
Ekasilicon was the name appointed by Mendeleev to the undiscovered germanium; germanium has similar chemical properties to silicon and tin.