Question

The element with atomic number $Z = 115$ will be placed in:
A. ${{\text{7}}^{{\text{th}}}}{\text{ period, I A group}}$
B. ${{\text{8}}^{{\text{th}}}}{\text{ period, IV A group}}$
C. ${{\text{7}}^{{\text{th}}}}{\text{ period, V A group}}$
D. ${{\text{6}}^{{\text{th}}}}{\text{ period, V B group}}$

Answer 1

Hint: The position of an element in periodic table of elements depends upon the electronic configuration of that element. From electronic configuration we can predict its period, group number and the block in which the element is present.

Complete step by step answer:
The periodic table of elements also known as simply periodic table is a tabular display of chemical elements. The basis of the arrangement of elements in tabular form is atomic number of elements. The elements are arranged in the tabular form to study the chemical properties. The electronic configuration of elements also plays an important role in the arrangement of elements in periodic tables.
Trick to predict the position of element in the periodic table:
Write down the electronic configuration of elements. The number of the maximum last shell in which the electron is filled is the period number of the element. The subshell of the atom in which the last electron exists is the block of the element. If the element is of $s - block$ then it is either of group one or group two. If the element is present in $p - block$ then the formula to find the group number is ($12 + {\text{number of electrons present in last p subshell}}$) and if the element is present in $d - block$ then the formula to find group number is ($2 + {\text{number of electrons present in (n - 1)d subshell}}$) where $n$ is the maximum number of shells present. The elements of $f - block$ are arranged experimentally, their group number is $3$ . If the atomic number of elements is above $100$ then we can find its group simply by subtracting $100$ from its atomic number and the group number of elements with the atomic number above $100$ is seven. So these concepts we will try to use in our problem.
We have given the atomic number $115$. The electronic configuration of this element is :
$\left[ {{\text{Rn}}} \right]5{f^{14}}6{d^{10}}7{s^2}7{p^3}$
The maximum number of the shell in electronic configuration is seven therefore the period number of element is also seven.
As we can see that it is $p - block$ element, so the formula to find the group number is $12 + {\text{number of electrons present in last p subshell}}$ and the number of electrons in last ${\text{p subshell}}$is three so the group number is $15(12 + 3)$ or we can say ${\text{V group}}$ .
The atomic number of the element is above 100 so we can use the other method also, we can subtract 100 from its atomic number and find out the group number.
$ \Rightarrow {\text{Group number = 115 - 100 = 15 or V A group}}$
So the element belongs to ${{\text{7}}^{{\text{th}}}}{\text{ period, V A group}}$.

So, the correct answer is Option C .

Note:
The periodic table is very useful in understanding the chemical properties of elements. It can be used to compare the different trends for elements. The trends like electronegativity, ionization enthalpy, atomic size etc. can be easily predicted with the help of periodic tables.