Chapter 2, Problem 2.112QP

(a)

Interpretation Introduction

Interpretation:

The electronic configuration and shorthand electronic configuration of biologically important $C{a}^{2+}ion$ has to be written.

Concept Introduction:

Electron configuration: The complete description of the atomic orbitals occupied by all the electrons in an atom or monoatomic ion is known as its electron configuration.

Explanation of Solution

Calcium is in Group $IIAor2$ and the atomic number is $20.$

$C{a}^{2+}ion$ Indicate that the ion has two less electrons than a neutral atom of Calcium.  The total number of electrons in $C{a}^{2+}ion$ can be calculated:

$\begin{array}{l}20e^{-}-2e^{-}=18e^{-}\\ electronsinCaelectronslosselectronsinC{a}^{2+}\end{array}$

The electron configuration is as follows:

  $1s^{2}2s^{2}2p^{6}3s^{2}3p^6$

Since $C{a}^{2+}ion$ is isoelectronic with $Ar$, Argon, all eighteen electrons of $C{a}^{2+}ion$ are indicated by the symbol $Ar$ in square brackets.  The shorthand electronic configuration for $C{a}^{2+}ion$ is $\left[Ar\right].$

(b)

Interpretation Introduction

Interpretation:

The electronic configuration and shorthand electronic configuration of biologically important $M{g}^{2+}ion$ has to be written.

Concept Introduction:

Refer to Part (a)

Explanation of Solution

Magnesium is in Group $IIAor\text{ 2}$ and the atomic number is $12.$

$M{g}^{2+}ion$ Indicate that the ion has two lessernumber of electrons than a neutral atom of Magnesium.  The total number of electrons in $M{g}^{2+}ion$ can be calculated:

$\begin{array}{l}12e^{-}-2e^{-}=10e^{-}\\ electronsinMgelectronslosselectronsinM{g}^{2+}\end{array}$

The electron configuration is as follows:

  $1s^{2}2s^{2}2p^6$

Since $M{g}^{2+}ion$ is isoelectronic with $Ne$, Neon, all ten electrons of $M{g}^{2+}ion$ are indicated by the symbol $Ne$ in square brackets.  The shorthand electronic configuration for $M{g}^{2+}ion$ is $\left[Ne\right].$

(c)

Interpretation Introduction

Interpretation:

The electronic configuration and shorthand electronic configuration of biologically important $K^{+}ion$ has to be written.

Concept Introduction:

Refer to Part (a)

Explanation of Solution

Potassium is in Group $IAor1$ and the atomic number is $19.$

$K^{+}ion$ Indicate that the ion has one less electron than a neutral atom of Potassium.  The total number of electrons in $K^{+}ion$ can be calculated:

$\begin{array}{l}19e^{-}-1e^{-}=18e^{-}\\ electronsinKelectronslosselectronsin{K}^{+}\end{array}$

The electron configuration is as follows:

  $1s^{2}2s^{2}2p^{6}3s^{2}3p^6$

Since $K^{+}ion$ is isoelectronic with $Ar$, Argon, all eighteen electrons of $K^{+}ion$ are indicated by the symbol $Ar$ in square brackets.  The shorthand electronic configuration for $K^{+}ion$ is $\left[Ar\right].$

(d)

Interpretation Introduction

Interpretation:

The electronic configuration and shorthand electronic configuration of biologically important $C{l}^{-}ion$ has to be written.

Concept Introduction:

Refer to Part (a)

Explanation of Solution

Potassium is in Group $IAor1$ and the atomic number is $19.$

$C{l}^{-}ion$ Indicate that the ion has one less electron than a neutral atom of Potassium.  The total number of electrons in $C{l}^{-}ion$ can be calculated:

$\begin{array}{l}17e^{-}+1e^{-}=18e^{-}\\ electronsinClelectrongainedelectronsinC{l}^{-}\end{array}$

The electron configuration is as follows:

  $1s^{2}2s^{2}2p^{6}3s^{2}3p^6$

Since $C{l}^{-}ion$ is isoelectronic with $Ar$, Argon, all eighteen electrons of $C{l}^{-}ion$ are indicated by the symbol $Ar$ in square brackets.  The shorthand electronic configuration for $C{l}^{-}ion$ is $\left[Ar\right].$