Chapter 8, Problem 45A

(a)

Interpretation Introduction

Interpretation: Whether ${\text{MgCl}}_{\text{2}}$ is ionic or covalent needs to be identified.

Concept Introduction: A covalent bond can be polar if the two atoms bonded together have electronegativity differences. Here, the atom with more electronegativity has a partial negative charge, and the atom with less electronegativity has a partial positive charge.

Explanation of Solution

The given compound is ${\text{MgCl}}_{\text{2}}$ . Here, Mg is a metal and Cl is a non-metal. Mg has 2 valence electrons and Cl has 7 valence electrons. Here, Mg can transfer its 2 electrons to each Cl atom to form ${\text{Mg}}^{2+}$ ion and two ${\text{Cl}}^{-}$ ions are formed. Thus, one Mg and two Cl ions combine to form ${\text{MgCl}}_{\text{2}}$ . Since the complete transfer of electrons from Mg to Cl takes place thus, they form ionic bonds and ${\text{MgCl}}_{\text{2}}$ is an ionic compounds.

(b)

Interpretation Introduction

Interpretation: Whether ${\text{Na}}_{\text{2}}\text{S}$ is ionic or covalent needs to be identified.

Concept Introduction: A covalent bond is formed between two non-metallic atoms by sharing of electron pairs. On the other hand, an ionic bond is formed between a metal and a non-metal by the complete transfer of electrons.

Explanation of Solution

The given compound is ${\text{Na}}_{\text{2}}\text{S}$ . Here, Na is a metal and S is a non-metal. The number of valence electrons in Na is 1 and that in S is 6. Here, 2 Na atoms can transfer their 2 electrons to 1 S atom to form 2 ${\text{Na}}^{+}$ ions and 1 ${\text{S}}^{2-}$ ion. Since the bond between Na and S is formed after the complete transfer of electrons, it is an ionic bond and ${\text{Na}}_{\text{2}}\text{S}$ so formed is an ionic compound.

(c)

Interpretation Introduction

Interpretation: Whether ${\text{H}}_{\text{2}}\text{O}$ is ionic or covalent needs to be identified.

Concept Introduction: A covalent bond is formed between two non-metallic atoms by sharing of electron pairs. On the other hand, an ionic bond is formed between a metal and a non-metal by the complete transfer of electrons.

Explanation of Solution

The given compound is ${\text{H}}_{\text{2}}\text{O}$ . Here, hydrogen and oxygen both are non-metals. The bond formed between H and O is due to sharing of electron pairs between them. The two O-H bonds are covalent in nature and ${\text{H}}_{\text{2}}\text{O}$ is a covalent bonds.

(d)

Interpretation Introduction

Interpretation: Whether ${\text{H}}_{\text{2}}\text{S}$ is ionic or covalent needs to be identified.

Concept Introduction: A covalent bond is formed between two non-metallic atoms by sharing of electron pairs. On the other hand, an ionic bond is formed between a metal and a non-metal by the complete transfer of electrons.

Explanation of Solution

The given compound is ${\text{H}}_{\text{2}}\text{S}$ . Here, hydrogen and sulfur both are non-metals. The bond formed between H and S is due to sharing of electron pairs between them. The two S-H bonds are covalent in nature and ${\text{H}}_{\text{2}}\text{S}$ is a covalent bonds.