Question

Calculate number of valence electrons and non-valence electrons in 5.6 ml of $S{{O}_{2}}$ gas.

Answer 1

Hint: From electronic configuration of the elements we can calculate the total number of electrons present in them.
The electronic configuration of Sulphur is \[1{{s}^{2}}2{{s}^{2}}2{{p}^{6}}3{{s}^{2}}3{{p}^{4}}\]
The electronic configuration of Oxygen is \[1{{s}^{2}}2{{s}^{2}}2{{p}^{4}}\]

Complete Solution :
- In the question it is asked to calculate the number of valence electrons and non-valence electrons in 5.6 ml of $S{{O}_{2}}$ gas.
- Before going to calculate the number of valence and non-valence electrons, we should calculate the numbers of molecules present in 5.6 ml of $S{{O}_{2}}$ gas.
- Therefore the formula to calculate the number of molecules in 5.6 ml of $S{{O}_{2}}$ gas is as follows.
Number of molecules = (number of moles) (Avogadro number)
\[\begin{align}
  & =\frac{5.6}{22400}\times 6.023\times {{10}^{23}} \\
 & =1.50575\times {{10}^{20}}molecules \\
\end{align}\]

- Means 5.6 ml of $S{{O}_{2}}$ gas at STP contains $1.50575\times {{10}^{20}} molecules$ .
- Now coming to the concept of valence and non-valence electrons present in $S{{O}_{2}}$.
-Total number of electrons in one $S{{O}_{2}}$ molecule = 16 + 8 + 8 = 32.
- Number of valence electrons present in Sulphur = 6
- Number of valence electrons present in Oxygen = 6
- So, the total number of valence electrons in one $S{{O}_{2}}$ molecule is = 6 + 6 + 6 = 18.
- So, the number of non-valence electrons in one $S{{O}_{2}}$ molecule is = 32 - 18 = 14.
- Now we have to calculate the number of valence and non-valence electrons in $1.50575\times {{10}^{20}} molecules$ .

- The number of valence electrons in $1.50575\times {{10}^{20}}molecules$ of sulphur dioxide is
\[\begin{align}
 & =1.50575\times {{10}^{20}}\times 18 \\
 & =27.1035\times {{10}^{20}} \\
 & =2.71035\times {{10}^{21}} \\
\end{align}\]

- The number of non-valence electrons in $1.50575\times {{10}^{20}} molecules$ of sulphur dioxide is
\[\begin{align}
 & = 1.50575\times {{10}^{20}}\times 14 \\
 & = 21.0805\times {{10}^{20}} \\
 & = 2.10805\times {{10}^{21}} \\
\end{align}\]

Note: We are not supposed to calculate the number of valence and non-valence electrons in one sulphur dioxide molecule, we are supposed to calculate the number of valence and non-valence electrons in 5.6 ml of sulphur dioxide.