Chapter 2, Problem 2.59AP

The most common isotope of oxygen has a mass number of 16, but two other isotopes having mass numbers of 17 and 18 are also known. 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; (e) the element symbols using superscripts and subscripts.

Interpretation Introduction

Interpretation:

The number of protons for the three isotopes of Oxygen has to be given.

Concept Introduction:

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.

Explanation of Solution

Given,

The atomic number of Oxygen is $8.$

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

Thus the number of protons for three isotopes of Oxygen (Oxygen-16,oxygen-17 and oxygen-18) is $8.$

Interpretation Introduction

Interpretation:

The number of neutrons for the three isotopes of Oxygen has to be given.

Concept Introduction:

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.

Explanation of Solution

Given,

The mass number of three oxygen isotopes is $16,17,18.$

The number of protons in three Oxygen isotopes is $8.$

The mass number of Oxygen -16 can be calculated as,

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

  $\begin{array}{l}\text{Number}\text{of}\text{neutrons=A-Number}\text{of}\text{protons}\\ \text{Number}\text{of}\text{neutrons=16-8}\\ \text{Number}\text{of}\text{neutrons=8}\end{array}$

The mass number of Oxygen -16 is $8.$

The mass number of Oxygen -17 can be calculated as,

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

  $\begin{array}{l}\text{Number}\text{of}\text{neutrons=A-Number}\text{of}\text{protons}\\ \text{Number}\text{of}\text{neutrons=17-8}\\ \text{Number}\text{of}\text{neutrons=9}\end{array}$

The mass number of Oxygen -17 is $9.$

The mass number of Oxygen -18 can be calculated as,

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

  $\begin{array}{l}\text{Number}\text{of}\text{neutrons=A-Number}\text{of}\text{protons}\\ \text{Number}\text{of}\text{neutrons=18-8}\\ \text{Number}\text{of}\text{neutrons=10}\end{array}$

The mass number of Oxygen -18 is $10.$

Interpretation Introduction

Interpretation:

The number of electrons for the three isotopes of Oxygen has to be given.

Concept Introduction:

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 of Oxygen is $8.$

  $\text{Atomic number of an element=The number of electrons}$

Thus the number of electrons for three isotopes of Oxygen (Oxygen-16,oxygen-17 and oxygen-18) is $8.$

Interpretation Introduction

Interpretation:

The group number of Oxygen has to be given.

Explanation of Solution

The oxygen is placed as first element in group-16 of the periodic table and is considered among the main group elements.

Interpretation Introduction

Interpretation:

The isotopic symbol of three Oxygen isotopes has to be given.

Explanation of Solution

The isotopic symbol of Oxygen-16 is,

Given,

The atomic number is $8.$

The mass number is $16.$

The isotopic symbol of the Oxygen-16 is given by writing the atomic number on the subscript and the mass number on the superscript.  Thus, the isotopic symbol of Oxygen-16 is ${{}_{\text{8}}}^{\text{16}}\text{O}\text{.}$

The isotopic symbol of Oxygen-17 is,

Given,

The atomic number is $8.$

The mass number is $17.$

The isotopic symbol of the Oxygen-17 is given by writing the atomic number on the subscript and the mass number on the superscript.  Thus, the isotopic symbol of Oxygen-17 is ${{}_{\text{8}}}^{\text{17}}\text{O}\text{.}$

The isotopic symbol of Oxygen-18 is,

Given,

The atomic number is $8.$

The mass number is $18.$

The isotopic symbol of the Oxygen-18 is given by writing the atomic number on the subscript and the mass number on the superscript.  Thus, the isotopic symbol of Oxygen-18 is ${{}_{\text{8}}}^{\text{18}}\text{O}\text{.}$