Chapter 8, Problem 6STP

Interpretation Introduction

Interpretation: The electron dot structure for given molecules needs to be drawn.

Concept Introduction: An electron dot structure represents the arrangement of total valence electrons in a molecule. Here, electrons are represented as dots in pairs to show the lone pairs as well as the bond pairs.

Explanation of Solution

The molecules in the given example are as follows:

  ${\text{CH}}_{\text{4}}$ , ${\text{NCl}}_{\text{3}}$ , ${\text{H}}_{\text{2}}\text{S}$ and, $\text{HF}$

In ${\text{CH}}_{\text{4}}$ molecule, the C atom is bonded with 4 H atoms via a single bond. There is no lone pair of electrons on C and H atoms thus, all the electrons will be bond pairs. The total number of valence electrons in a molecule can be calculated by taking the sum of the number of valence electrons of C and H.

The valence electrons of C atom is 4 and that of H atom is 1. Thus, the total number of valence electrons will be:

  $\begin{array}{c}4+4\left(1\right)=4+4\\ =8\end{array}$

The arrangement of electrons can be represented as follows:

  

In ${\text{NCl}}_{\text{3}}$ , N atom is bonded with 3 Cl atoms via a single bond. There is one lone pair of electrons on the N atom and three lone pairs of electrons on the Cl atom. The total number of valence electrons can be calculated by taking the sum of valence electrons of N and Cl atom.

The number of valence electrons of N and Cl atom is 5 and 7 respectively. Thus, the total number of valence electrons will be:

  $\begin{array}{c}5+3\left(7\right)=5+21\\ =26\end{array}$

The arrangement of electrons can be represented as follows:

  

In ${\text{H}}_{\text{2}}\text{S}$ molecule, 2 H atoms are bonded with 1 S atom via single bonds. The valence electrons of H and S atom is 1 and 6 respectively. The total number of valence electrons can be calculated as follows:

  $2\left(1\right)+6=8$

Here, S has 2 lone pairs of electrons.

The arrangement of electrons can be represented as follows:

  

In the HF molecule, 1 H and 1 F atoms are bonded together via a single bond. The valence electrons of the H and F atom is 1 and 7 respectively. Thus, the total number of valence electrons will be 8. Here, F has 3 lone pairs of electrons. The arrangement of electrons can be represented as follows: