Question

If the atomic number of an element is 33, it will be placed in the periodic table in the
A– First group
B– Second Group
C– Fifth Group
D– Seventh Group

Answer 1

Hint: This question is based on the concept of Mendeleev periodic table, and the modern periodic table. Write the electronic configuration of an element having 33 atomic number, and then identify the group.

Complete step by step answer:
First, let us know the concept of assigning a group in the modern periodic table, it depends on the number of valence electrons
Now, we know the element with atomic number 33 is arsenic. Let us write the electronic configuration 1s${}^2$2s${}^2$2p${}^6$3s${}^2$3p${}^6$4s${}^2$3d${}^{10}$4p${}^3$
By looking at the electronic configuration, we can see that there are a total 30 electrons till 3d orbital, and the 3 electrons in the 4p orbital.
So, now we can say that there are 5 number of valence electrons.
Thus, according to modern periodic table it will belong to the group 15, but group 15 is not given in the options.
So, we will look according to the concept of Mendeleev periodic table then we can say it belongs to the group 5.
Thus, in the last, we can conclude that if the atomic number of an element is 33, it will be placed in the periodic table in the group 5.
Hence, the correct option is (C).

Note: There is no need of getting confused between the Mendeleev periodic table, and the modern periodic table. Both the concepts assign the group number according to the number of valence electrons, but in case of modern periodic table, the element having atomic number 33 belongs to the p-block elements, so the 10 will be added to the no. of valence electrons.