Question

Examples of elements belonging to s, p, d or f- block are given below. Identify the wrong example.

Answer 1

Hint: Write down the electronic configuration of the elements given in the options. Try to recall the general configuration of the 4 blocks, s, p, d and f. Try to match the general electronic configuration given against the element and its electronic configuration. The element whose electronic configuration does not match with the general electronic configuration is the answer.

Complete answer:
The elements of group 1 and group 2 of the modern periodic table are called s block elements. Group 1 consists of alkali metals and group 2 consists of group 2 elements. They are called s block elements because the last electron of the valent shell goes into s orbital. The elements have a general electronic configuration of $n{{s}^{1-2}}$.
The electronic configuration of caesium is $[Xe]\text{ 6}{{s}^{1}}$. This matches with the general electronic configuration of s - block elements. Hence option (A) is true.
The elements of group 13 to 18 of the modern periodic table are called p block elements. The starting elements of these groups are nonmetals and we proceed down the group the elements are metals. Group 18 is called the noble gases group as all the elements of the group are inert due to complete octet. The elements of p block have a general outer configuration of $n{{s}^{2}}n{{p}^{1-6}}$.
The electronic configuration of barium is $[Xe]\text{ 6}{{s}^{2}}$. The electronic configuration of barium does not match with the general configuration of p block elements. Hence option (B) is false.
The elements of group 3 to 12 of the modern periodic table are called d block elements. The elements of this group have a tendency to show more than one valency. The elements of d block have a general electronic configuration of \[(n-1){{d}^{1-10}}n{{s}^{2}}\].
The electronic configuration of Chromium is $[Ar]\text{ 3}{{d}^{4}}4{{s}^{2}}$. The electronic configuration of chromium is similar to the general configuration of d block elements. Hence option (C) is true.
F block elements are divided into two series, namely lanthanoids and actinoids. The elements of group 14 are referred to as inner transition elements. The general electronic configuration is $(n-2){{f}^{1-14}}(n-1){{d}^{1-10}}n{{s}^{2}}$.
The electronic configuration of Thorium is $[Rn]5{{f}^{1}}6{{d}^{1}}7{{s}^{2}}$. The electronic configuration of thorium is similar to general configuration of f block. Hence option (D) is true.

Therefore, the wrong example is option (B).

Note:
Elements of b block are commonly referred to as transition metals. However not all metals present in d blocks are transition metals. Metals like zinc, cadmium and mercury are d block elements however they are not transition metals as they have filled d orbitals and do not exhibit variable valency.