Chapter 9, Problem 9.75QE

(a)

Interpretation Introduction

Interpretation:

The Lewis structure of ${\text{SeF}}_6$ has to be determined. Also, whether ${\text{SeF}}_6$ is an odd-electron molecule, an electron-deficient molecule, or an expanded valence shell molecule has to be determined.

Concept Introduction:

A covalent bond is a bond that is formed from the mutual sharing of electrons between atoms. Lewis structures are representations of the covalent bond. In this, Lewis symbols show how the valence electrons are present in the molecule.

Steps to write Lewis structures are as follows:

1. The skeleton structure with single bonds between all bonded atoms has to be written

2. Sum the valence electrons of the atoms in the molecule.

(a) For cations, one electron is subtracted for each positive charge.

(b) For anions, one electron is added for each negative charge.

3. Subtract two electrons from total number of valence electrons for each bond in the skeleton structure.

4. Count the number of electrons required to satisfy the octet rule for each atom in the structure. If the number of electrons needed is less than the number remaining, add one bond for every two electrons needed between atoms to attain an octet.

5. The remaining electrons are placed as lone pairs on atoms that need them to satisfy the octet rule.

Some compounds exceed an octet around the central atom and are called as expanded valence shell molecule. The central atom belongs to third and fourth periods. In this, the molecule has electrons more than eight electrons in Lewis structure.

The electron-deficient molecule is a molecule in which there are less electrons than electrons available that join atoms in the molecule through covalent bonds. In electron-deficient molecules, atoms have more stable orbitals in the valence shell than the electrons.

Odd-electron molecules are atoms with unpaired electrons. They are also called as radicals. Radicals do not obey the octet rule because they do not have completely filled $s$ and $p$ subshell.

(b)

Interpretation Introduction

Interpretation:

The Lewis structure of ${\text{BBr}}_{\text{3}}$ has to be determined. Also, whether ${\text{BBr}}_{\text{3}}$ is an odd-electron molecule, an electron-deficient molecule, or an expanded valence shell molecule has to be determined.

Concept Introduction:

Refer to part (a)

(c)

Interpretation Introduction

Interpretation:

The Lewis structure made from ${\text{NO}}_{\text{2}}$ has to be determined. Also, whether ${\text{NO}}_{\text{2}}$ is an odd-electron molecule, an electron-deficient molecule, or an expanded valence shell molecule has to be determined.

Concept Introduction:

Refer to part (a)