Question

Two elements X and Y have following electronic configuration
X $1{s^2},2{s^2},2{p^6};3{s^2},3{p^6};4{s^2}$
Y $1{s^2},2{s^2},2{p^6};3{s^2},3{p^5}$
The expected compound formed by combination of X and Y will be expressed as:
A) $X{Y_2}$
B) ${X_5}{Y_2}$
C) ${X_2}{Y_5}$
D) $X{Y_5}$

Answer 1

In chemistry, periodic tables play a vital role. In the periodic table there are totally $118$ elements. In the periodic table there are totally $18$ columns and $7$ rows. The columns are called groups. Hence, $18$ groups in the periodic table. The rows are called periods. Hence, totally $7$ period in the table. The valency is nothing but the number of electrons that donate or accept the atom to attain the stable electronic configuration.

Complete answer:
The valency of the atom is nothing but the number of electrons gain or loss to attain the stable electronic configuration in the molecule.
The given data is
Two elements X and Y have following electronic configuration
X $1{s^2},2{s^2},2{p^6};3{s^2},3{p^6};4{s^2}$
Y $1{s^2},2{s^2},2{p^6};3{s^2},3{p^5}$
The total number of electrons in X is $20$. The valency of X is $2$, because X wants to become stable, which means it will donate the two electrons.
The total number of electrons in Y is $17$. The valency of Y is $1$, because Y want to become stable, which means it will accept one electron from others.
The expected compound formed by combination of X and Y will be $X{Y_2}$, because X wants to donate the two electrons to become stable. So, it donates two electrons to the two Y and Y also becomes stable to accept the one electron from X.
According to the above discussion, we conclude the expected compound formed by combination of X and Y will be expressed as $X{Y_2}$.

Hence, option A is the correct answer.

Note:
We have to know that the atomic number of the element is nothing but the number of electrons or number of protons. The mass number of the atom is nothing but the sum of the number of protons and number of neutrons. The atomic number of the atom is equal to the number of protons or the number of electrons. In every atom the number of protons and the number of electrons are equal. The stable electronic configuration in the second period is $10$. The stable electronic configuration in the third period is $18$.