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 $$1s^{2}2s^{2}2p^{6}3s^{2}3p^4$$
The electronic configuration of Oxygen is $$1s^{2}2s^{2}2p^4$$

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)
$$\begin{array}{rl}& =\frac{5.6}{22400}\times 6.023\times {10}^{23}\\ & =1.50575\times {10}^{20}molecules\end{array}$$

- 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
$$\begin{array}{rl}& =1.50575\times {10}^{20}\times 18\\ & =27.1035\times {10}^{20}\\ & =2.71035\times {10}^{21}\end{array}$$

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

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.