Question

Which is mismatched regarding the position of the element as given below?
(A) $X\left( {Z = 89} \right)$ f-block, ${6^{th}}$ period
(B) $\;Y\left( {Z = 100} \right)$ f-block, ${7^{th}}$ period
(C) $\;Z\left( {Z = 115} \right)$ d-block, ${7^{th}}$ period
(D) Both $1$ and $3$

Answer 1

Chemical elements were arranged in the periodic table, which is divided into four blocks namely s, p, d, and f blocks. The f-block elements are nothing but lanthanides with atomic numbers $57$ to $71$ and actinides $89$ to $103$ . The d-block elements consist of groups from $13$ to $18$ .

Complete answer:
The periodic table is the representation of chemical elements arranged in the increasing order of atomic numbers in the vertical columns and horizontal rows. The vertical columns were known as groups and the horizontal rows were known as periods. There are a total of $7$ periods and $18$ groups in the periodic table.
The atomic number with $Z = 89$ is actinium. The chemical symbol of actinium is $Ac$ , it is placed in the f-block in the ${7^{th}}$ period. Thus, the given answer is not matched.
The atomic number with $Z = 100$ is fermium. The chemical symbol of fermium is $Fm$ , it is placed in the f-block in the ${7^{th}}$ period. Thus, the given answer is matched.
The atomic number with $Z = 115$ is Moscovium. The chemical symbol of Moscovium is $Mc$ , it is placed in the p-block but not d-block in the ${7^{th}}$ period. Thus, the given answer is not matched.
Thus, both $1$ and $3$ are mismatched regarding the position of the element.
Option $4$ is the correct one.

Note:
Actinium has the atomic number of $89$ . The last electron enters into d-block only, but not f-orbital. as the f-block is started before filling up the d-block. The element actinium is placed in actinide series i.e., in f-block. Sometimes, it is placed in d-block only.