According to Mendeleev's Periodic Table, which elements’ properties matched up remarkably well with eka-silicon?

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Accepted Answer

Mendeleev placed “eka-silicon” directly below silicon in Group 14 and predicted its properties (valency 4, oxide formula like $EO_2$, atomic weight and density estimates). When germanium was discovered, its properties matched these predictions very closely: atomic weight $\approx 72.6$ (Mendeleev had estimated about $\approx 72$) and density about $5.47\ 	ext{g/cm}^3$ (close to his estimate $\approx 5.5\ 	ext{g/cm}^3$).

Why the others are wrong:
- Gallium (option a) matched Mendeleev's eka-aluminium, not eka-silicon.
- Scandium (option b) corresponds to eka-boron.
- Titanium (option c) is in a different group and not predicted as eka-silicon.

Thus the element that matched eka-silicon is Germanium (option d).

FINAL_ANSWER: d

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