Answer: Germanium (eka-silicon, discovered 1886).
- A Germanium (eka-silicon, discovered 1886)
- B Silicon, whose properties were already well known before Mendeleev
- C Gallium, discovered independently without matching a gap prediction
- D Scandium, discovered before Mendeleev published his periodic law
Correct answer: A. Germanium (eka-silicon, discovered 1886)
Explanation: Germanium's discovery in 1886 closely matched Mendeleev's eka-silicon predictions for atomic mass, density, and oxide properties.
The complete modern periodic table (118 elements). Image: Cepheus et al., Public Domain, via Wikimedia Commons.
Concept context
The periodic table organises all 118 elements by atomic number and similar properties. Study periodic trends like atomic radius, ionization energy, and electronegativity, and learn how an element's position predicts its behaviour.
Read the full Classification of Elements and Periodicity in Properties notes →