Question

If the atomic number of an element is 33, it will be placed in the periodic table in the:
A. 1 group
B. 13 group
C. 15 group
D. 7 group

Answer 1

Periodic table contains 18 groups and 7 periods. For an element of a given atomic number, first we have to write the electronic configuration. By looking at this configuration we can find period, group and block. So the period will be the same as the principal quantum number of the valence shell. Block of an element is given by the orbital in which the last electron enters. The group of an element is obtained from the number of electrons in the valence shell or penultimate shell which is given as follows:
a) For S block elements, the group number is equal to the number of valence electrons.
b)For P block elements, the group number is equal to the 10 added to the number of electrons in the valence shell.
c)For d block elements, the group number is equal to the sum electrons in the penultimate subshell $\left( {n - 1} \right)$ and valence shell.
d)f block elements belong to group 3 and 4. Lanthanides belongs to group 3 and actinides belong to group 4.

Complete step by step answer:
The atomic number of element given in the question is 33, So the electronic configuration is $1{s^{ - 2}}2{s^2}2{p^6}3{s^2}3{p^6}4{s^2}3{d^{10}}4{p^3}$ .
The given element belongs to period 4 which is the principal quantum number. The last electron enters in the p subshell so this element belongs to the p block. We know that for p block elements the group number is equal to the 10 added to the number of electrons in the valence shell. Here the valence shell is the N shell which contains 4s and 4p orbitals.
Number of valence electrons =5.
Therefore its group will be 10+5=15.

Hence the correct answer is (C). That is, the given element belongs to group 15.

Additional information:
S orbital can accommodate a maximum of 2 electrons. P orbital can accommodate 6 and d can accommodate 10 electrons
First element of every group departs from the general properties , this is known as anomalous behavior.
Anomalous behavior of boron includes its small size, high ionization energy, covalent nature, non -metallic character etc.
P block is unique in terms of having all types of elements: metals, nonmetals and metalloids.
The reluctance of ns electrons to take part in the bond formation is known as inert pair effect.
Some of the elements of P block such as Sn, Pb etc. show different oxidation states due to this inert pair effect.
Deviations from the normally expected electron filling are observed in transition elements.
This is due to the very little energy difference between $\left( {n - 1} \right)$ d and ns orbitals and relatively higher stability of half filled and completely filled orbitals.
f block elements are more reactive than transition elements.

Note:
The shells are named as K, L, M, N etc. The outermost shell is called valence shell, the electrons present in it are the valence electrons. If a student carelessly takes valence electrons as 3, since there are 3 electrons in 4p subshell, the answer may go wrong .So important thing we have to note here that the valence shell here contains 4s and 4p subshell. The electrons in these 2 subshells give the number of electrons in the valence shell. 1 and 2 group elements are called S block elements. The group 3 to 12 belongs to d block elements also called transition elements. Group 13 to 18 called p block elements. The f block elements are also called inner transition elements or third transition series. They have partially filled f orbital.