Question

Transition elements are also known as ____________.

• A. $d$ - block elements
• B. $f$ - block elements
• C. $s$ - block elements
• D. None of these

Answer 1

The correct option is A $d$ - block elements

The transition elements are also known as the $d$-block elements because while the outermost level contains at most two electrons, their next to outermost main levels have incompletely filled $d$ sub-orbitals, which are filled-up progressively ongoing across the periodic table from $8$ to $18$ electrons. The filling of the $d$ sub-orbitals of the transition elements across a row of the periodic table is not always regular.

Hence, the correct option is $\text{A}$