Chapter 2, Problem 2.41QE

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:

Atomic number is given as 11, number of electrons is given as 10, and number of neutrons is given as 12.  Total number of protons present in the nucleus is the atomic number.  Therefore, the number of protons present is 11.

Mass number is the sum of number of protons and number of neutrons.  This can be calculated as shown below.

    $\begin{array}{c}A=Z+n\\ =11+12\\ =23\end{array}$

Charge can be calculated by finding the difference between the number of protons and electrons as shown below.

    $\begin{array}{c}\text{Charge}=\text{Number}\text{of}\text{protons}-\text{Number}\text{of}\text{electrons}\\ \text{=11}-10\\ =+1\end{array}$

Atomic number is given as 11.  The element with atomic number 11 is found to be sodium which has a symbol as $\text{Na}$.

For entry 2:

Symbol is given as ${}^{\text{40}}{\text{Ca}}^{\text{2+}}$.  As the given ion is a calcium ion, the atomic number is found to be 20.  This in turn means that the total number of protons is 20.

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.

    $\begin{array}{c}A=Z+n\\ n=A-Z\\ =40-20\\ =20\end{array}$

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

    $\begin{array}{c}\text{Charge}=\text{Number}\text{of}\text{protons}-\text{Number}\text{of}\text{electrons}\\ \text{2=20}-\text{Number}\text{of}\text{electrons}\\ \text{Number}\text{of}\text{electrons}=20-2\\ =18\end{array}$

For entry 3:

Number of protons is given as 35.  This means that the atomic number of the species is 35.  The element with atomic number 35 is found to be bromine with the symbol of $\text{Br}$.

Mass number is the sum of number of protons and number of neutrons.  From the mass number given as 81, the number of neutrons can be calculated as shown below.

    $\begin{array}{c}A=Z+n\\ n=A-Z\\ =81-35\\ =46\end{array}$

Charge is given as $1-$.  This means the number of electrons is 1 more than that of the protons.

    $\begin{array}{c}\text{Charge}=\text{Number}\text{of}\text{protons}-\text{Number}\text{of}\text{electrons}\\ -\text{1=35}-\text{Number}\text{of}\text{electrons}\\ \text{Number}\text{of}\text{electrons}=35+1\\ =36\end{array}$

For entry 4:

Number of protons is given as 52.  This means that the atomic number of the species is 52.  The element with atomic number 52 is found to be tellurium with the symbol of $\text{Te}$.

Mass number is the sum of number of protons and number of neutrons.  This can be calculated as shown below.

    $\begin{array}{c}A=Z+n\\ =52+76\\ =128\end{array}$

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

    $\begin{array}{c}\text{Charge}=\text{Number}\text{of}\text{protons}-\text{Number}\text{of}\text{electrons}\\ -\text{2=52}-\text{Number}\text{of}\text{electrons}\\ \text{Number}\text{of}\text{electrons}=52+2\\ =54\end{array}$

Complete table can be given as shown below.

Symbol	${}^{\text{23}}{\text{Na}}^{\text{+}}$	${}^{\text{40}}{\text{Ca}}^{\text{2+}}$	${}^{\text{81}}{\text{Br}}^{-}$	${}^{\text{128}}{\text{Te}}^{2-}$
Atomic number	$11$	$20$	$35$	$52$
Mass number	$23$	$40$	$81$	$128$
Charge	$+1$	$+2$	$1-$	$2-$
Number of protons	$11$	$20$	$35$	$52$
Number of electrons	$10$	$18$	$36$	$54$
Number of neutrons	$12$	$20$	$46$	$76$