Chapter 3, Problem 54P

What is the charge on the anion Z in each of the following ionic compounds?

1. $\text{BaZ}$

${\text{Al}}_{\text{2}}{\text{Z}}_{\text{3}}$

${\text{Li}}_{\text{3}}\text{Z}$

${\text{Hg}}_{\text{2}}\text{Z}$

Interpretation Introduction

(a)

Interpretation:

The positive charge on Ba & the overall charge of BaZ should be considered to determine the charge on Z.

Concept introduction:

An ionic compound forms by the mutual attraction of 2 oppositely charged ions.

Answer to Problem 54P

Charge of Z = -2

Explanation of Solution

An ionic compound forms by the mutual attraction of 2 oppositely charged ions. The ion containing the positive charge is known as the cation. The ion containing the negative charge is known as the anion.

Usually in an ionic formula cation is mentioned in the left & anion in the right of the formula. Consider the given ionic compound of BaZ. In here the atom forming the cation should be Ba & the atom forming the anion should be Z. (It is wrong to mention Ba as the cation & Z as the anion, as they don't contain any charge)

A cation is formed by removing 1 or few electrons from an atom. As electrons are negatively charged, the removal of electrons (negative charges) gives a positive charge to the rest of the atom.

Consider Ba.

The electron configuration of Ba is,

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 6s²

The outer shell is 6s. The 2 electrons in 6s can be removed. After removing this 2 electrons Ba gets a +2 charge, and can be written as Ba²⁺.

In a simple, stable ionic compound, the overall charge is zero. So, in BaZ overall charge is zero. That means the +2 charge in Ba²⁺ should be neutralized by the negative charge of the anion.

As (+2) + (-2) = 0, the charge on anion, Z should be -2. So it should be Z-2.

Interpretation Introduction

(b)

Interpretation:

The positive charge on 2 Al ions & the overall charge of Al₂Z₃should be considered to determine the charge on 3 Z atoms.

Concept introduction:

An ionic compound forms by the mutual attraction of 2 oppositely charged ions.If a simple ionic compound having more than one cations of same type, the charge of all the cations should be same. This concept is common for anions also.

Answer to Problem 54P

Charge of Z = -2

Explanation of Solution

An ionic compound forms by the mutual attraction of 2 oppositely charged ions. The ion with the positive charge is known as the cation. The ion with the negative charge is known as the anion.

Usually in an ionic formula cation is mentioned in the left & anion in the right of the formula. Consider the given ionic compound of Al₂Z₃. In here the atom forming the cation should be Al (Aluminum)& the atom forming the anion should be Z.

A cation is formed by removing 1 or few electrons from an atom. As electrons are negatively charged, the removal of electrons (negative charges) gives a positive charge to the rest of the atom.

Consider Al.

The electron configuration of Al is,

1s² 2s² 2p⁶ 3s² 3p¹

The outer shell has 3s & 3p. Usually the removal of electrons from the outer shell is easier, because they are the located away from the nucleus. So the 2 electrons in 3s& 1 electron in 3p can be removed. After removing this 3 electrons Al gets a +3chargeand can be written as Al³⁺.

  $Al \to A{l}^{3+}+3e \left(electronsareindicatedase\right)$

In a simple, stable ionic compound, the overall charge is zero. So in Al₂Z₃ overall charge is zero.

If a simple ionic compound having more than one cations of same type, the charge of all the cations should be same. There are 2 Al in the compound. Those 2 should be Al³⁺. So the overall positive charge will be +6. This +6 charge in 2 Al³⁺ should be neutralized by the negative charge of the anion.

There are 3 Z anions in Al₂Z_3.These 3 anions should be similar in charge. So the +6 should be divided with in the 3 Z ions. So the charge on Z should be -2.

This can be explained by the following simple calculation. Assume the charge on 1 Z ion is x. so the charge on 3 Z ions is 3x.

Charge on cations + Charge on anions = 0 (Because the ionic compound has no net charge)

  $\begin{array}{l}(+3\times 2)+3x=0\hfill \\ 3x =-6\hfill \\ x =-6/2\hfill \\ x =-2\hfill \end{array}$

Interpretation Introduction

(c)

Interpretation:

The positive charge on 3 Li ions& the overall charge of Li₃Z should be considered to determine the charge on the Z atom.

Concept introduction:

An ionic compound forms by the mutual attraction of 2 oppositely charged ions. If a simple ionic compound having more than one cations of same type, the charge of all the cations should be same.

Answer to Problem 54P

Charge of Z = -3

Explanation of Solution

An ionic compound forms by the mutual attraction of 2 oppositely charged ions. The ion with the positive charge is known as the cation. The ion with the negative charge is known as the anion.

Usually in an ionic formula cation is mentioned in the left & anion in the right of the formula. Consider the given ionic compound of Li₃Z. In here the atom forming the cation should be Li (Lithium) & the atom forming the anion should be Z.

A cation is formed by removing 1 or few electrons from an atom. As electrons are negatively charged, the removal of electrons (negative charges) gives a positive charge to the rest of the atom.

Consider Li which is located in the first group of the periodic table.

The electron configuration of Li is,

1s² 2s¹

The outer shell is 2s. Usually the removal of electrons from the outer shell is easier, because they are the located away from the nucleus. So the attraction of these electrons to the nucleus is low.

So the single electron in 2s can be easily removed. After removing this electronLi gets a +1charge, and can be written as Li⁺.

  $Li \to L{i}^{+}+e(electronsareindicatedase)$

In a simple, stable ionic compound, the overall charge is zero. If there is an overall charge, it is mentioned at the right side of the compound. So in Li₃Z overall charge is zero.

If a simple ionic compound having more than one cations of same type, the charge of all the cations should be same. And also the most common oxidation state of Li is +1.There are 3 Li s in the compound. Those 3 should be Li⁺. So the overall positive charge will be +3, which is neutralized by the only one Z anion.

So the charge on Z should be -3.

This can be explained by the following simple calculation. Assume the charge on Z ion is x.

Charge on cations + Charge on anions = 0 (Because the ionic compound should has no net charge)

  $\begin{array}{l}(+1\times 3)+x=0 \\ x =-3\end{array}$

Interpretation Introduction

(d)

Interpretation:

The positive charge on Hg& the overall charge of Hg₂Z should be considered to determine the charge on Z. apart from that formation of colloidal Hg should be studied.

Concept introduction:

An ionic compound forms by the mutual attraction of 2 oppositely charged ions.

Formation of Colloidal mercury is formed with the reaction between Hg²⁺& Hg.

Answer to Problem 54P

Charge of Z = -2

Explanation of Solution

An ionic compound forms by the mutual attraction of 2 oppositely charged ions. The ion with the positive charge is known as the cation. The ion with the negative charge is known as the anion.

Usually in an ionic formula cation is mentioned in the left & anion in the right of the formula. Consider the given ionic compound of Hg₂Z. In here the atom forming the cation should be Hg (Mercury) & the atom forming the anion should be Z.

Mercury/Hg has the special ability to form dimeric Hg. This is known as the formation of colloidal Hg. The related cation is $H{g}_2^{2+}$ . Formation of this cation can be explained by the following reaction.

  $H{g}^{2+}+Hg \rightleftharpoons Hg{ }_2^{2+}$

A mercury (Hg) atom reacts with Hg²⁺ to form $Hg{ }_2^{2+}$

In a simple, stable ionic compound, the overall charge is zero. If there is an overall charge, it is mentioned at the right side of the compound. So in Hg₂Z overall charge is zero. $H{g}_2^{2+}$ have a charge of +2. This charge should be neutralized by the anion form by Z.

  $Z+2e \to Z^{2-} \left(electronsareindicatedase\right)$

So,the charge on Z should be -2.