Chapter 8, Problem 41A

(a)

Interpretation Introduction

Interpretation: Whether nitrogen is found in Earth’s atmosphere as molecules or individual atoms needs to be explained.

Concept Introduction: Elements can exist as molecules or individual atoms depending on the number of valence electrons present in the atom of the element. If sharing of electron pairs is required, atoms of the element are present in combined form as molecules in the atmosphere. For atoms with a complete octet, they are present as individual atoms.

Explanation of Solution

In the Earth’s atmosphere, nitrogen gas is present as molecules. The molecular formula of nitrogen gas is ${\text{N}}_{\text{2}}$ , This is because a nitrogen atom has 5 valence electrons thus, it needs three electrons to complete its octet as per the octet rule. Two nitrogen atoms can share three electron pairs to form a triple covalent bond. Thus, nitrogen is found as a molecule, not as an individual atom.

(b)

Interpretation Introduction

Interpretation: Whether oxygen is found in Earth’s atmosphere as molecules or individual atoms needs to be explained.

Concept Introduction: Elements can exist as molecules or individual atoms depending on the number of valence electrons present in the atom of the element. If sharing of electron pairs is required, atoms of the element are present in combined form as molecules in the atmosphere. For atoms with a complete octet, they are present as individual atoms.

Explanation of Solution

In the Earth’s atmosphere, oxygen gas is present as molecules. The molecular formula of oxygen gas is ${\text{O}}_{\text{2}}$ , This is because an oxygen atom has 6 valence electrons, it needs two electrons to complete its octet as per the octet rule. Two oxygen atoms can share two electron pairs to form a double covalent bond. Thus, oxygen is found as a molecule, not as an individual atom.

(c)

Interpretation Introduction

Interpretation: Whether argon is found in Earth’s atmosphere as molecules or individual atoms needs to be explained.

Concept Introduction: Elements can exist as molecules or individual atoms depending on the number of valence electrons present in the atom of the element. If sharing of electron pairs is required, atoms of the element are present in combined form as molecules in the atmosphere. For atoms with a complete octet, they are present as individual atoms.

Explanation of Solution

Argon is found as an individual atom in the Earth’s atmosphere. The number of valence electrons in an argon atom is 8 thus, it has a complete octet. It does not bond with any other atom to complete its octet.