Chapter 2, Problem 2.127QE

Interpretation Introduction

Interpretation:

Partial columns has to be filled in the table given in problem statement.

Concept Introduction:

Each and every element present in the Periodic table has a unique name.  Some of the elements are named considering their atomic number.  In order to represent the elements in a short form, atomic symbols are used.  Generally the first two letters of the element name will be used as symbol where the first letter is in upper case.

Chemical names are represented as atomic symbols.  In the symbols, the mass number and atomic number are shown.  The complete symbol for an element can be represented as shown below.

Atomic number is the total number of protons present in the atom of an element.  Mass number is the total number of protons and neutrons present in nucleus of an atom.

Explanation of Solution

For entry 1:

Number of protons is given as 31.  This means that the atomic number of the species is 31.  The element with atomic number 31 is found to be gallium with the symbol of $\text{Ga}$.

Mass number is the sum of number of protons and number of neutrons.  From the mass number given as 70, the number of neutrons can be calculated as shown below.

    $\begin{array}{c}A=Z+n\\ n=A-Z\\ =70-31\\ =39\end{array}$

Number of electrons is given as 28.  The charge on the species can be calculated as shown below.

    $\begin{array}{c}\text{Charge}=\text{Number}\text{of}\text{protons}-\text{Number}\text{of}\text{electrons}\\ \text{=31}-\text{28}\\ =3+\end{array}$

The symbol for the species is given as $\text{G}{\text{a}}^{\text{3+}}$.

For entry 2:

Number of electrons is given as 42.  Charge on the species is given as $\text{3+}$.  From this the number of protons can be calculated as shown below.

    $\begin{array}{c}\text{Charge}=\text{Number}\text{of}\text{protons}-\text{Number}\text{of}\text{electrons}\\ \text{3+=Number}\text{of}\text{protons}-\text{42}\\ \text{Number}\text{of}\text{protons}=42+3\\ =45\end{array}$

Number of protons is found as 45.  This means that the atomic number of the species is 45.  The element with atomic number 45 is found to be rhodium with the symbol of $\text{Rh}$.

Mass number is the sum of number of protons and number of neutrons.  From the mass number given as 103, the number of neutrons can be calculated as shown below.

    $\begin{array}{c}A=Z+n\\ n=A-Z\\ =103-45\\ =58\end{array}$

The symbol for the species is given as $\text{R}{\text{h}}^{\text{3+}}$.

For entry 3:

Atomic number is given as 49.  This means that the number of protons in the species is 49.  The element with atomic number 49 is found to be indium with the symbol of $\text{In}$.

The charge on the species is given as $1+$.  The number of electrons can be calculated as shown below.

    $\begin{array}{c}\text{Charge}=\text{Number}\text{of}\text{protons}-\text{Number}\text{of}\text{electrons}\\ \text{+1=49}-\text{Number}\text{of}\text{electrons}\\ \text{Number}\text{of}\text{electrons}=49-1\\ =48\end{array}$

Mass number is the sum of number of protons and number of neutrons.  Number of neutrons is given as 65.  From this mass number can be calculated as shown below.

    $\begin{array}{c}A=Z+n\\ =49+65\\ =114\end{array}$

The symbol for the species is given as $\text{I}{\text{n}}^{\text{1+}}$.

For entry 4:

Symbol is given as ${}^{\text{28}}{\text{Si}}^{\text{2-}}$.  As the given ion is a silicon ion, the atomic number is found to be 14.  This in turn means that the total number of protons is 14.

Mass number is the sum of number of protons and number of neutrons.  From the mass number given as 40 in the symbol, the number of neutrons can be calculated as shown below.

    $\begin{array}{c}A=Z+n\\ n=A-Z\\ =28-14\\ =14\end{array}$

Charge is given as $2-$ in the symbol.  This means the number of electrons is 2 more than that of the protons.

    $\begin{array}{c}\text{Charge}=\text{Number}\text{of}\text{protons}-\text{Number}\text{of}\text{electrons}\\ \text{-2=14}-\text{Number}\text{of}\text{electrons}\\ \text{Number}\text{of}\text{electrons}=14+2\\ =16\end{array}$

Complete table can be given as shown below.

Symbol	${}^{\text{70}}{\text{Ga}}^{\text{3+}}$	${}^{\text{103}}{\text{Rh}}^{\text{3+}}$	${}^{\text{114}}{\text{In}}^{+}$	${}^{\text{28}}{\text{Si}}^{2-}$
Atomic number	$31$	$45$	$49$	$14$
Mass number	$70$	$103$	$114$	$28$
Charge	$+3$	$+3$	$+1$	$-2$
Number of protons	$31$	$45$	$49$	$14$
Number of electrons	$28$	$42$	$48$	$16$
Number of neutrons	$39$	$58$	$65$	$14$