Chapter 9, Problem 126A

(a)

Interpretation Introduction

Interpretation: The number of protons and electrons in the given ion needs to be determined.

Concept Introduction: Metals are electropositive and they tend to form cations by losing electrons. On the other hand, non-metals are electronegative and tend to accept electrons. Thus they form anions.

Answer to Problem 126A

The most stable ionic form of magnesium is ${\text{Mg}}^{\text{2+}}$ . An ${\text{Mg}}^{\text{2+}}$ ion has 12 protons and 10 electrons.

Explanation of Solution

The most stable ion of magnesium ${\text{Mg}}^{\text{2+}}$ , is formed by losing two electrons from the magnesium atom. Mg with atomic number 12 has 12 protons and 12 electrons. So ${\text{Mg}}^{\text{2+}}$ contains 12 protons and 10 electrons.

(b)

Interpretation Introduction

Interpretation: The number of protons and electrons in the given ion needs to be determined.

Concept Introduction: Metals are electropositive and they tend to form cations by losing electrons. On the other hand, non-metals are electronegative and tend to accept electrons. Thus they form anions.

Answer to Problem 126A

Bromide ion is a monovalent ion. It has 35 protons and 36 electrons.

Explanation of Solution

A bromide ion is formed when a bromine atom accepts one electron. A bromine atom with atomic number 35 contains 35 electrons and 35 protons. The addition of one more electron makes a bromide ion, with 35 protons and 36 electrons.

(c)

Interpretation Introduction

Interpretation: The number of protons and electrons in the given ion needs to be determined.

Concept Introduction: Metals are electropositive and they tend to form cations by losing electrons. On the other hand, non-metals are electronegative and tend to accept electrons. Thus they form anions.

Answer to Problem 126A

Strontium belongs to alkaline earth metals and forms ${\text{Sr}}^{\text{2+}}$ ions. Strontium ions contain 38 protons and 36 electrons.

Explanation of Solution

Strontium ions are formed when a strontium atom with 38 protons and 38 electrons loses two electrons. Thus ${\text{Sr}}^{\text{2+}}$ contains 38 protons and 36 electrons.

(d)

Interpretation Introduction

Interpretation: The number of protons and electrons in the given ion needs to be determined.

Concept Introduction: Metals are electropositive and they tend to form cations by losing electrons. On the other hand, non-metals are electronegative and tend to accept electrons. Thus they form anions.

Answer to Problem 126A

Sulphur is a non-metal which tends to form divalent ions. Sulphide ions contain 16 protons and 18 electrons.

Explanation of Solution

Sulphur has an atomic number of 16 and it contains 16 protons and 16 electrons. When two more electrons are added to the sulphur atom, we get a sulphide ion $\left({\text{S}}^{\text{2-}}\right)$ . So, a sulphide ion contains 16 protons and 18 electrons.