Question

Valence electrons in the elements X and Y are \[3\] and \[6\] what is the formula of the compound formed from X and Y?
A.\[{X_2}{Y_3}\]
B.\[{X_2}{Y_4}\]
C.\[{X_2}{Y_3}\]
D.None of these

Answer 1

Hint: We must have to remember that the electrons present in the outermost shell of an atom are known as valence electrons. For example, the number of valence electrons of oxygen is equal to six. Two electron in $2s$ subshell and four electron present in the $2p$subshell. If the outer shell is not closed, these valence electrons can be included in the formation of chemical bonds. The number of electrons will be different for each element which is present in the different groups and periods.

Complete answer:
The molecular formula of the compound formed from X and Y is equal to \[{X_2}{Y_3}\].
The valence number of electrons in the elements X and Y are \[3\] and \[6\]respectively. Here, an equal number of electrons has to be donated. So,
$3 \times X = \left( {8 - 6} \right) \times Y$
By rearranging the equation,
\[\dfrac{X}{Y} = \dfrac{2}{3}\]
Here, the number of X elements present in the compound is equal to three and the number of Y is equal to two. Therefore, the molecular formula of the compound formed from X and Y is equal to \[{X_2}{Y_3}\]. Hence, option (A) is correct.
The molecular formula of the compound is not equal to \[{X_2}{Y_4}\]. Hence, option (B) is incorrect.
The molecular formula of the compound is not equal to \[{X_2}{Y_3}\]. Hence, option (C) is incorrect.
The molecular formula of the compound is equal to \[{X_2}{Y_3}\]. Hence, option (D) is incorrect.

Hence, option (A) is correct.

Note:
We have to remember that the molecular formula specifies the numbers of atoms present in the molecule of a chemical substance. And the molecular formula is the same as that of the empirical formula. The molecular formula mainly contains the chemical symbols of the corresponding element and it has numeric subscripts to express the number of atoms present in a molecule. Therefore, the molecular formula will show the actual number of atoms present in a molecule.