Chapter 10, Problem 10.19P

(a)

Interpretation Introduction

Interpretation:

Lewis structure for ${\text{BH}}_3$ is to be drawn. Also, the type of octet-rule exception is to be determined.

Concept introduction:

Steps to draw the Lewis structure of the molecule are as follows:

Step 1: Find the central atom and place the other atoms around it. The atom in a compound which has the lowest group number or lowest electronegativity considered as the central atom.

Step 2: Calculate the total number of valence electrons.

Step 3: Connect the other atoms around the central atoms to the central atom with a single bond and lower the value of valence electrons by 2 of every single bond.

Step 4: Allocate the remaining electrons in pairs so that each atom can get 8 electrons.

The octet rule is defined that every element shares an octet (8 electrons) in their outermost electron shell to form compounds. In other words, the element that obeys the octet rule must have surrounded by eight electrons. If an atom has less than eight electrons, it is said to be electron deficient and if an atom has more than eight electrons around it, it is said to be the atom has an expanded octet.

There are three important exceptions of the octet rule:

1. A molecule with electron-deficient atoms.

2. A molecule with the odd-electron atoms.

3. An atom with expanded valence shells.

(b)

Interpretation Introduction

Interpretation:

Lewis structure for ${\text{AsF}}_4^{-}$ is to be drawn. Also, the type of octet-rule exception is to be determined.

Concept introduction:

Steps to draw the Lewis structure of the molecule are as follows:

Step 1: Find the central atom and place the other atoms around it. The atom in a compound which has the lowest group number or lowest electronegativity considered as the central atom.

Step 2: Calculate the total number of valence electrons.

Step 3: Connect the other atoms around the central atoms to the central atom with a single bond and lower the value of valence electrons by 2 of every single bond.

Step 4: Allocate the remaining electrons in pairs so that each atom can get 8 electrons.

The octet rule is defined that every element shares an octet (8 electrons) in their outermost electron shell to form compounds. In other words, the element that obeys the octet rule must have surrounded by eight electrons. If an atom has less than eight electrons, it is said to be electron deficient and if an atom has more than eight electrons around it, it is said to be the atom has an expanded octet.

There are three important exceptions of the octet rule:

1. A molecule with electron-deficient atoms.

2. A molecule with the odd-electron atoms.

3. An atom with expanded valence shells.

(c)

Interpretation Introduction

Interpretation:

Lewis structure for ${\text{SeCl}}_4$ is to be drawn. Also, the type of octet-rule exception is to be determined.

Concept introduction:

Steps to draw the Lewis structure of the molecule are as follows:

Step 1: Find the central atom and place the other atoms around it. The atom in a compound which has the lowest group number or lowest electronegativity considered as the central atom.

Step 2: Calculate the total number of valence electrons.

Step 3: Connect the other atoms around the central atoms to the central atom with a single bond and lower the value of valence electrons by 2 of every single bond.

Step 4: Allocate the remaining electrons in pairs so that each atom can get 8 electrons.

The octet rule is defined that every element shares an octet (8 electrons) in their outermost electron shell to form compounds. In other words, the element that obeys the octet rule must have surrounded by eight electrons. If an atom has less than eight electrons, it is said to be electron deficient and if an atom has more than eight electrons around it, it is said to be the atom has an expanded octet.

There are three important exceptions of the octet rule:

1. A molecule with electron-deficient atoms.

2. A molecule with the odd-electron atoms.

3. An atom with expanded valence shells.