Question

An element has atomic number $115$ . Where will you place this element in the modern periodic table?

Answer 1

Hint : There are many elements in the periodic table. Each element has its own configuration. They have been assigned according to their properties by our scientist. So, to answer this question we should have the exact knowledge of the configuration, every period and every group, actually the whole structure we have to keep in mind.

Complete Step By Step Answer:
Firstly we calculate the number of elements up-to sixth period as $= 2 + 8 + 18 + 18 + 32 = 86$
As we have to find the position for the $115th$ element so we should subtract the number of elements we get above from the element which has been asked by us. Therefore, the number of extra electrons in the atom with atomic number $115 = 115 - 86 = 29$ .Therefore, there are $29$ extra electrons present in the atom. Now, we find the configuration of the seventh period having $29$ electrons and that is equal to $7{s^2}5{f^{14}}6{d^{10}}7{p^3}$ . Therefore, we can see that the element having atomic number $115$ will be found at the cross of $15th$ group and $7th$ period.

Note :
The modern periodic table is a tabular display of the chemical elements which are arranged on the basis of atomic number, electronic configuration, and recurring chemical properties. There are seven periods and eighteen groups present in the modern periodic table. Some of the groups have accepted names such as group $17$ elements are known as halogens and group $18$ elements are known as noble gases. Similarly, group $1$ elements are known as earth metals whereas group $2$ elements are known as alkaline earth metals.