The correct answer is (C) : Eu (Atomic Number 63)
Yb+2 is 4f14
Eu+2 is 4f7
but Eu+2 is more stable than Yb+2 because
\(E°_{Eu|Eu^{2+}} > E°_{Yb|Yb^{2+}}\)
The correct order of basicity of oxides of vanadium is
Lanthanoids are at the top of these two-row, while actinoids are at the bottom row.
Lanthanoids are inclusive of 14 elements, with atomic numbers 58-71:
These elements are also called rare earth elements. They are found naturally on the earth, and they're all radioactively stable except promethium, which is radioactive. A trend is one of the interesting properties of the lanthanoid elements, called lanthanide contraction.