Question

Element having atomic number ${\text{33}}$ belongs to this group?
A) $III$
B) $IV$
C) $V$
D) $VI$

Answer 1

The concept of this question belongs to the modern periodic table. As we know that in periodic table sequencing of elements is done on the basis of their atomic number, as they are categorized according to their properties.

Complete step by step answer:

1. First of all from the concept we know that a group is always similar to the number of valence electrons of a given element. Write electronic configuration for the given atomic number. The atomic number ${\text{33}}$ belongs to element Arsenic (As).
   Electronic Configuration $\left( {As} \right):{\text{ }}1{s^2}2{s^2}2{p^6}3{s^2}3{p^6}4{s^2}3{d^{10}}4{p^3}$
2. Now as it is noticed from the electronic configuration, that there are ${\text{30}}$ electrons till ${\text{3d}}$ orbital and it is a p- block element with the ${\text{3}}$electrons in ${\text{4p}}$ orbital. So, there are ${\text{5}}$ valence electrons.
3. Then according to the Mendeleev periodic table concept, it belongs to the group ${\text{5}}$, because the no of valence electrons is ${\text{5}}$.
4. Therefore, an element having atomic number ${\text{33}}$ belongs to this group $V$ which shows option C as the correct choice.
   Hence, the statement is false.

Note:
Mendeleev periodic table is based on the properties of elements as dependent on atomic mass, elements are arranged based on their increasing atomic mass while modern table based on atomic number as it considers as the fundamental property and element are arranged based on their increasing atomic numbers. There are total ${\text{7}}$ groups and ${\text{6}}$ periods in Mendeleev’s periodic table while ${\text{18}}$ groups and ${\text{7}}$ periods in modern periodic table. No place allotted for isotopes in Mendeleev’s periodic table while in modern periodic table isotopes are kept in the same place due to their atomic numbers being the same.