Chapter F, Problem B.3E

(a)

Interpretation Introduction

Interpretation:

The number of protons, neutrons and electrons present in the atom of boron-11 has to be given.

Concept Introduction:

Atomic number for each and every element is a unique one.  This is the total number of protons that is present in an atom.  As the atom is electrically neutral, it can also be said that the total number of electrons is the atomic number.  Atomic number is represented by the symbol Z.

$\text{Atomic number}\text{=}\text{number of protons}\text{=}\text{number of electrons}$

Mass number is the sum of the number of protons and neutrons inside the nucleus of an atom.  This gives the number of subatomic particle present inside the nucleus.  Mass number is represented by the symbol A.

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

From atomic number and mass number, the number of each sub atomic particle can be found.

$\begin{array}{l}\text{Number of protons}\text{=}\text{Atomic number}\text{=}Z\\ \text{Number of electrons}\text{=}\text{Atomic number}\text{=}Z\\ \text{Number of neutrons}\text{=}\text{Mass}\text{number - Atomic number}\text{=}A-Z\end{array}$

Complete chemical symbol notation can be given as.

An element is a pure substance that cannot be broken by ordinary chemical reactions into simpler substances.  All the atoms in an element will have the same atomic number.  The electrons only take part in the chemical reaction while the nucleus does not.  Hence, the atomic number (number or protons) does not change and it characterizes an atom.

Explanation of Solution

Given atom is boron-11.  From this it is understood that the atomic number is $5$ and mass number is $11$.  The number of protons, electrons and neutrons can be found as shown below,

  $\begin{array}{l}\text{Number of protons}\text{=}\text{Atomic number}\text{=}Z\\ \text{Number of electrons}\text{=}\text{Atomic number}\text{=}Z\\ \text{Number of neutrons}\text{=}\text{Mass}\text{number - Atomic number}\text{=}A-Z\end{array}$

Atomic number is given as $5$ and mass number is given as $11$.

  $\begin{array}{l}\text{Number of protons}\text{=Atomic number}\text{=}5\\ \text{Number of electrons}\text{=Atomic number}\text{=}5\\ \text{Number of neutrons}\text{=Mass}\text{number - Atomic number}\text{=}11-5\\ =6\end{array}$

Therefore, the number of protons is $5$ , number of electrons is $5$, and number of neutrons is $6$.

(b)

Interpretation Introduction

Interpretation:

The number of protons, neutrons and electrons present in the atom of ${}^{\text{10}}\text{B}$ has to be given.

Concept Introduction:

Refer part (a).

Explanation of Solution

Given atom is ${}^{\text{10}}\text{B}$.  From this it is understood that the atomic number is $5$  and mass number is $10$.  The number of protons, electrons and neutrons can be found as shown below,

  $\begin{array}{l}\text{Number of protons}\text{=}\text{Atomic number}\text{=}Z\\ \text{Number of electrons}\text{=}\text{Atomic number}\text{=}Z\\ \text{Number of neutrons}\text{=}\text{Mass}\text{number - Atomic number}\text{=}A-Z\end{array}$

Atomic number is given as $5$ and mass number is given as $10$.

  $\begin{array}{l}\text{Number of protons}\text{=Atomic number}\text{=}5\\ \text{Number of electrons}\text{=Atomic number}\text{=}5\\ \text{Number of neutrons}\text{=Mass}\text{number - Atomic number}\text{=}10-5\\ =5\end{array}$

Therefore, the number of protons is $5$ , number of electrons is $5$, and number of neutrons is $5$.

(c)

Interpretation Introduction

Interpretation:

The number of protons, neutrons and electrons present in the atom of phosphorus-31 has to be given.

Concept Introduction:

Refer part (a).

Explanation of Solution

Given atom is phosphorus-31.  From this it is understood that the atomic number is $15$  and mass number is $31$.  The number of protons, electrons and neutrons can be found as shown below,

  $\begin{array}{l}\text{Number of protons}\text{=}\text{Atomic number}\text{=}Z\\ \text{Number of electrons}\text{=}\text{Atomic number}\text{=}Z\\ \text{Number of neutrons}\text{=}\text{Mass}\text{number - Atomic number}\text{=}A-Z\end{array}$

Atomic number is given as $15$ and mass number is given as $31$.

  $\begin{array}{l}\text{Number of protons}\text{=Atomic number}\text{=}15\\ \text{Number of electrons}\text{=Atomic number}\text{=}15\\ \text{Number of neutrons}\text{=Mass}\text{number - Atomic number}\text{=}31-15\\ =16\end{array}$

Therefore, the number of protons is $15$ , number of electrons is $15$, and number of neutrons is $16$.

(d)

Interpretation Introduction

Interpretation:

The number of protons, neutrons and electrons present in the atom of ${}^{\text{238}}\text{U}$ has to be given.

Concept Introduction:

Refer part (a).

Explanation of Solution

Given atom is ${}^{\text{238}}\text{U}$.  From this it is understood that the atomic number is $92$  and mass number is $238$.  The number of protons, electrons and neutrons can be found as shown below,

  $\begin{array}{l}\text{Number of protons}\text{=}\text{Atomic number}\text{=}Z\\ \text{Number of electrons}\text{=}\text{Atomic number}\text{=}Z\\ \text{Number of neutrons}\text{=}\text{Mass}\text{number - Atomic number}\text{=}A-Z\end{array}$

Atomic number is given as $92$ and mass number is given as $236$.

  $\begin{array}{l}\text{Number of protons}\text{=Atomic number}\text{=}92\\ \text{Number of electrons}\text{=Atomic number}\text{=}92\\ \text{Number of neutrons}\text{=Mass}\text{number - Atomic number}\text{=}238-92\\ =146\end{array}$

Therefore, the number of protons is $92$ , number of electrons is $92$, and number of neutrons is $146$.