The atomic number of gadolinium (\(Gd\)) is \(64\) and its electronic configuration is as
\(Gd(64):[Xe]4f^{7}\,5d^{1}6s^{2}\)
It is a member of the rare earth elements group. It is silvery white, and a ductile metal with high melting and boiling point.
So, the correct answer is (D): gadolinium
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.