Question

The atomic numbers of transition elements of $6d$ series of ${}^{\prime }{d}^{\prime }$ block elements:

• A. $89$
• B. $104$
• C. $105$
• D. all of the above

Answer 1

The correct option is D all of the above

$6d$ series consists of elements $Ac$ (atomic number $89$) and those beyond Rutherfordium/Kurchatovium (atomic number $104$). These elements lie in the seventh period. This period is still incomplete. At present this series consist of $Ac\left(89\right)$, $Ku\left(104\right)$, $Ha\left(105\right)$ and $Unh\left(106\right)$ (four elements). These elements involve the gradual filling of $6d$ orbitals.