Chapter 2, Problem 2.61AP

(a)

Interpretation Introduction

Interpretation:

The number of protons, the number of neutrons and the number of electrons in ${{}_{\text{13}}}^{\text{27}}\text{Al}$ has to be given.

Concept introduction;

Atomic number (Z):

Atomic number of an element is the number of protons found in the nucleus of every atom of that element.

Mass number (A):

Mass number of an element is defined as the total number of protons and neutrons in an atom.

Protons:

A proton is one of three main particles that make up the atom.  Protons are a tiny, dense region at the center of the atom.  Protons have a positive electrical charge of $+1$ and a mass of 1 atomic mass which is $\text{1}{\text{.62×10}}^{\text{-27}}$ kilograms.

Neutrons:

Atoms of all elements except for most atoms of hydrogen have neutrons in their nucleus. Unlike protons and electrons, which are electrically charged, neutrons have no charge they are electrically neutral.

Electrons:

Electrons have an electric charge of $\text{-1}$, which is equal but opposite to the charge of a proton, which have an electric charge of $\text{+1}\text{.}$  All atoms have the same number of electrons as protons, so the positive and negative charges cancel out making atoms electrically neutral.

Explanation of Solution

Given,

The atomic number is $13.$

The mass number is $27.$

The number of proton is,

  $\text{Atomic number of an element=Number of protons}$

Thus, the number of protons in the atom is $13.$

The number of electrons is,

  $\text{Number}\text{of}\text{electrons}\text{=}\text{Number}\text{of}\text{Protons}$

Thus, the number of electrons in the atom is $13.$

The number of neutrons can be calculated as,

  $\text{A=Number}\text{of}\text{protons}\text{+}\text{Number}\text{of}\text{neutrons}$

  $\begin{array}{l}\text{Number}\text{of}\text{neutrons=A-Number}\text{of}\text{protons}\\ \text{Number}\text{of}\text{neutrons=27-13}\\ \text{Number}\text{of}\text{neutrons=14}\end{array}$

The number of neutrons in an atom is $\text{14}\text{.}$

(b)

Interpretation Introduction

Interpretation:

The number of protons, the number of neutrons and the number of electrons in ${{}_{\text{17}}}^{\text{35}}\text{Cl}$ has to be given.

Concept introduction;

Refer to part (a).

Explanation of Solution

Given,

The atomic number is $17.$

The mass number is $35.$

The number of proton is,

  $\text{Atomic number of an element=Number of protons}$

Thus, the number of protons in the atom is $17.$

The number of electron is,

  $\text{Number}\text{of}\text{electrons}\text{=}\text{Number}\text{of}\text{Protons}$

Thus, the number of electrons in the atom is $17.$

The number of neutrons can be calculated as,

  $\text{A=Number}\text{of}\text{protons}\text{+}\text{Number}\text{of}\text{neutrons}$

  $\begin{array}{l}\text{Number}\text{of}\text{neutrons=A-Number}\text{of}\text{protons}\\ \text{Number}\text{of}\text{neutrons=35-17}\\ \text{Number}\text{of}\text{neutrons=18}\end{array}$

The number of neutrons in an atom is $\text{18}\text{.}$

(c)

Interpretation Introduction

Interpretation:

The number of protons, the number of neutrons and the number of electrons in ${{}_{\text{16}}}^{\text{34}}\text{S}$ has to be given.

Concept introduction;

Refer to part (a).

Explanation of Solution

Given,

The atomic number is $16.$

The mass number is $34.$

The number of proton is,

  $\text{Atomic number of an element=Number of protons}$

Thus, the number of protons in the atom is $16.$

The number of electron is,

  $\text{Number}\text{of}\text{electrons}\text{=}\text{Number}\text{of}\text{Protons}$

Thus, the number of electrons in the atom is $16.$

The number of neutrons can be calculated as,

  $\text{A=Number}\text{of}\text{protons}\text{+}\text{Number}\text{of}\text{neutrons}$

  $\begin{array}{l}\text{Number}\text{of}\text{neutrons=A-Number}\text{of}\text{protons}\\ \text{Number}\text{of}\text{neutrons=34-16}\\ \text{Number}\text{of}\text{neutrons=18}\end{array}$

The number of neutrons in an atom is $\text{18}\text{.}$