Chapter 4, Problem 38A

Interpretation Introduction

Interpretation: The total number of electrons in the given ionsneeds to be determined.

Concept introduction:Charge tells the number of electrons more or less than number of electrons present in the neutral state. For a neutral atom, charge is zero but if an electron is removed, atom becomes positive charge and if an electron is added, atom becomes negative charge.

Answer to Problem 38A

  $\begin{array}{l}{\text{Se}}^{\text{2-}}=38\\ {\text{S}}^{\text{2-}}=18\\ {\text{P}}^{\text{3-}}=18\\ {\text{O}}^{\text{2-}}=10\\ {\text{N}}^{\text{3-}}=10\\ {\text{I}}^{\text{-}}=54\\ {\text{F}}^{\text{-}}=10\\ {\text{Cl}}^{\text{-}}=18\\ {\text{Br}}^{\text{-}}=36\\ {\text{At}}^{\text{-}}=86\end{array}$

Explanation of Solution

To find the total number of electrons present in the negative ions given, first note the atomic numbers of the ions.

Then, note the charge given and add them to the atomic number.

Therefore, $\text{Electron}\text{present}=\text{Atomic}\text{number}+\text{Charge}$

Negative ions	Atomic number	Total number of electrons
${\text{Se}}^{\text{2-}}$	34	36
${\text{S}}^{\text{2-}}$	16	18
${\text{P}}^{\text{3-}}$	15	18
${\text{O}}^{\text{2-}}$	8	10
${\text{N}}^{\text{3-}}$	7	10
${\text{I}}^{\text{-}}$	53	54
${\text{F}}^{\text{-}}$	9	10
${\text{Cl}}^{\text{-}}$	17	18
${\text{Br}}^{\text{-}}$	35	36
${\text{At}}^{\text{-}}$	85	86

Conclusion

Positive ions means it will loss electrons and negative ions means it will gain electrons to reach the noble gas configuration.