Chapter 1, Problem 1.1P

While the most common isotope of nitrogen has a mass number of $14$ (nitrogen- $14$), a radioactive isotope of nitrogen has a mass number of $13$ (nitrogen- $13$). Nitrogen- $13$ is used in PET (positron emission tomography) scans by physicians to monitor brain activity and diagnose dementia. For each isotope, give the following information: (a) the number of protons; (b) the number of neutrons; (c) the number of electrons in the neutral atom; (d) the group number; and (e) the number of valence electrons.

Interpretation Introduction

(a)

Interpretation: The number of protons in nitrogen-$13$ and nitrogen-$14$ is to be predicted.

Concept introduction: Isotopes of a particular element have different number of neutrons. The mass number of an atom is the total number of protons and neutrons in the nucleus. In a neutral atom, number of protons in a nucleus is equal to the number of electrons.

Answer to Problem 1.1P

The number of protons in nitrogen-$13$ isotope is $7$. The number of protons in nitrogen-$14$ isotope is $7$.

Explanation of Solution

Atomic number of nitrogen is $7$. Hence, the number of protons in nitrogen-$13$ isotope is $7$ and nitrogen-$14$ isotope is $7$.

Conclusion

The number of protons in nitrogen-$13$ isotope is $7$.The number of protons in nitrogen-$14$ isotope is $7$.

Interpretation Introduction

(b)

Interpretation: The number of protons in nitrogen-$13$ and nitrogen-$14$ is to be predicted.

Concept introduction: Isotopes of a particular element have different number of neutrons. The mass number of an atom is the total number of protons and neutrons in the nucleus. In a neutral atom, number of protons in a nucleus is equal to the number of electrons.

Answer to Problem 1.1P

The number of neutrons in nitrogen-$13$ is $6$ and the number of neutrons is nitrogen-14 is $7$.

Explanation of Solution

Number of neutrons is calculated by the formula,

$\text{Mass}\text{number}=\text{Number of}\text{protons}+\text{Number of}\text{neutrons}$

The number of protons in nitrogen-$13$ isotope is $7$.

Substitute the value of number of protons in nitrogen-$13$ and mass number in the above formula. .

$\begin{array}{rll}13& =& 7+\text{Number of}\text{neutrons}\\ \text{Number of}\text{neutrons}& =& 13-7\\ & =& 6\end{array}$

Hence, the number of neutrons is nitrogen-$13$ is 6.

The number of protons in nitrogen-$14$ isotope is $7$.

Substitute the value of number of protons and mass number in the above formula.

$\begin{array}{rll}14& =& 7+\text{Number}\text{of}\text{neutrons}\\ \text{Number of}\text{neutrons}& =& 14-7\\ & =& 7\end{array}$

Hence, the number of neutrons is nitrogen-14 is $7$.

Conclusion

The number of neutrons in nitrogen-$13$ is $6$ and the number of neutrons is nitrogen-14 is $7$.

Interpretation Introduction

(c)

Interpretation: The number of electrons in the neutral atom is to be predicted.

Concept introduction: Isotopes of a particular element have different number of neutrons. The mass number of an atom is the total number of protons and neutrons in the nucleus. In a neutral atom, number of protons in a nucleus is equal to the number of electrons.

Answer to Problem 1.1P

The number of electrons in the neutral atom is 7.

Explanation of Solution

Atomic number of nitrogen is $7$. The number of protons in nitrogen-$13$ isotope is $7$ and nitrogen-$14$ isotope is $7$. Number of protons is equal to number of electrons in neutral atom. Hence, the number of electrons in the neutral atom is 7.

Conclusion

The number of electrons in neutral atom is 7.

Interpretation Introduction

(d)

Interpretation: The group number of Nitrogen atom is to be predicted.

Concept introduction: Isotopes of a particular element have different number of neutrons. The mass number of an atom is the total number of protons and neutrons in the nucleus. In a neutral atom, number of protons in a nucleus is equal to the number of electrons.

Answer to Problem 1.1P

The group number of Nitrogen atom is $5\text{A}$.

Explanation of Solution

In the periodic table of elements, each column is identified by a group number, Arabic $1\text{to}8$ or Roman $\text{(I}\text{toVIII)}$ numeral followed by the letter A or B. The group number of nitrogen atom is $5\text{A}$.

Conclusion

The group number of Nitrogen atom is $5\text{A}$.

Interpretation Introduction

(e)

Interpretation: The number of valence electrons in the isotopes of Nitrogen is to be predicted.

Concept introduction: Isotopes of a particular element have different number of neutrons. The mass number of an atom is the total number of protons and neutrons in the nucleus. In a neutral atom, number of protons in a nucleus is equal to the number of electrons.

Answer to Problem 1.1P

The number of valence electrons in Nitrogen atom is $5$.

Explanation of Solution

The outermost electrons in an atom are called valence electrons. The valence electrons are more loosely held than the electrons which are closer to the nucleus, and they participate in chemical reactions. The group number of second-row elements indicates its number of valence electrons. The group number of Nitrogen atom is $5\text{A}$. Hence, the number of valence electrons is $5$.

Conclusion

The number of valence electrons in Nitrogen atom is $5$.