Chapter 1, Problem 55AE

Identify each of the following elements. Give the number of protons and neutrons in each nucleus.

a. $\text{X}$

b. $\text{X}$

c. $\text{X}$

d. $\text{X}$

Interpretation Introduction

To determine: The element and the number of protons and neutrons in the element.

Interpretation: Symbols of unknown elements are given. The elements and the number of protons and electrons in the elements are to be determined.

Concept introduction: In a neutral atom, the number of protons and electrons are same and equal to the atomic number of that atom but in an ion, they are different in number depending on the charge on the ion. The sum of the number of protons and number of neutrons is equal to the mass number of that atom or ion.

Answer to Problem 55AE

The element is phosphorus $\left(\text{P}\right)$ and the number of protons and electrons are $\underset{\_}{15}\text{and}\underset{\_}{16}$, respectively.

Explanation of Solution

Given

Symbol of the unknown element is ${}_{15}^{31}X$.

An atom in represented by the symbol as,

${}_Z^{A}X$

Where,

• $\text{X}$ is symbol of atom.
• $A$ is mass number of atom.
• $Z$ is atomic number of atom.

Atomic number $Z=15$

In the periodic table, atomic number $15$ corresoponds to Phosphorus $\left(\text{P}\right)$.

Thus, the unknown element is Phosphorus $\left(\text{P}\right)$.

Atomic number of an atom is equal to the number of proton in the atom.

$\begin{array}{c}p=Z\\ =\underset{\_}{15}\end{array}$

Number of neutrons is calculated using the formula,

$A=p+n$

Where,

• $A$ is atomic mass.
• $p$ is number of protons.
• $n$ is number of neutrons.

Substitute the values of $A$ and $p$ in the above equation.

$\begin{array}{c}31=15+n\\ n=\underset{\_}{16}\end{array}$

Conclusion

The unknown element is Phosphorus $\left(\text{P}\right)$.

The number of proton is $15$ and the number of neutron is $16$.

Interpretation Introduction

To determine: The element and the number of protons and neutrons in the element.

Answer to Problem 55AE

The element is Iodine $\left(\text{I}\right)$ and the number of protons and electrons are $\underset{\_}{53}\text{and}\underset{\_}{74}$, respectively.

Explanation of Solution

Given

Symbol of the unknown element is ${}_{53}^{127}X$.

An atom in represented by the symbol as,

${}_Z^{A}X$

Where,

• $\text{X}$ is symbol of atom.
• $A$ is mass number of atom.
• $Z$ is atomic number of atom.

Atomic number $Z=53$

In the periodic table, atomic number $53$ corresoponds to Iodine $\left(\text{I}\right)$.

Thus, the unknown element is Iodine $\left(\text{I}\right)$. 

Atomic number of an atom is equal to the number of proton in the atom.

$\begin{array}{c}p=Z\\ =\underset{\_}{53}\end{array}$

Number of neutrons is calculated using the formula,

$A=p+n$

Where,

• $A$ is atomic mass.
• $p$ is number of protons.
• $n$ is number of neutrons.

Substitute the values of $A$ and $p$ in the above equation.

$\begin{array}{c}127=53+n\\ n=\underset{\_}{74}\end{array}$

Conclusion

The unknown element is Iodine $\left(\text{I}\right)$.

The number of proton is $53$ and the number of neutron is $74$.

Interpretation Introduction

To determine: The element and the number of protons and neutrons in the element.

Answer to Problem 55AE

The element is Potassium $\left(\text{K}\right)$ and the number of protons and electrons are $\underset{\_}{19}\text{and}\underset{\_}{20}$, respectively.

Explanation of Solution

Given

Symbol of the unknown element is ${}_{19}^{39}X$.

An atom in represented by the symbol as,

${}_Z^{A}X$

Where,

• $\text{X}$ is symbol of atom.
• $A$ is mass number of atom.
• $Z$ is atomic number of atom.

Atomic number $Z=19$

In the periodic table, atomic number $53$ corresoponds to Potassium $\left(\text{K}\right)$.

Thus, the unknown element is Potassium $\left(\text{K}\right)$. 

Atomic number of an atom is equal to the number of proton in the atom.

$\begin{array}{c}p=Z\\ =\underset{\_}{19}\end{array}$

Number of neutrons is calculated using the formula,

$A=p+n$

Where,

• $A$ is atomic mass.
• $p$ is number of protons.
• $n$ is number of neutrons.

Substitute the values of $A$ and $p$ in the above equation.

$\begin{array}{c}39=19+n\\ n=\underset{\_}{20}\end{array}$

Conclusion

The unknown element is Potassium $\left(\text{K}\right)$.

The number of proton is $19$ and the number of neutron is $20$.

Interpretation Introduction

To determine: The element and the number of protons and neutrons in the element.

Answer to Problem 55AE

The element is Ytterbium $\left(\text{Yb}\right)$ and the number of protons and electrons are $\underset{\_}{70}\text{and}\underset{\_}{103}$, respectively.

Explanation of Solution

Given

Symbol of the unknown element is ${}_{70}^{173}X$.

An atom in represented by the symbol as,

${}_Z^{A}X$

Where,

• $\text{X}$ is symbol of atom.
• $A$ is mass number of atom.
• $Z$ is atomic number of atom.

Atomic number $Z=70$

In the periodic table, atomic number $70$ corresoponds to Ytterbium $\left(\text{Yb}\right)$.

Thus, the unknown element is Ytterbium $\left(\text{Yb}\right)$. 

Atomic number of an atom is equal to the number of proton in the atom.

$\begin{array}{c}p=Z\\ =\underset{\_}{70}\end{array}$

Number of neutrons is calculated using the formula,

$A=p+n$

Where,

• $A$ is atomic mass.
• $p$ is number of protons.
• $n$ is number of neutrons.

Substitute the values of $A$ and $p$ in the above equation.

$\begin{array}{c}173=70+n\\ n=\underset{\_}{103}\end{array}$

Conclusion

The unknown element is Ytterbium $\left(\text{Yb}\right)$.

The number of proton is $70$ and the number of neutron is $103$.