Chapter U1, Problem 9STP

Interpretation Introduction

Interpretation:

The number of neutrons and protons present in the nucleus of an atom of ${}_{\text{88}}^{\text{226}}\text{Ra}$ should be determined.

Concept introduction:

The general atomic symbol of an element is:

${}_{\text{Z}}^{\text{A}}\text{X}$

Where A is mass number of an atom, Z is atomic number, and X is the atomic symbol of an element.

Answer to Problem 9STP

The number of protons is $\text{88}$ and number of neutrons is $\text{138}$ present in the nucleus of an atom of ${}_{\text{88}}^{\text{226}}\text{Ra}$.

Explanation of Solution

The protons and neutrons of an atom are present in the nucleus of an atom whereas the electrons are always moving around the nucleus of an atom that is they possess kinetic energy. Thus, the number of protons and neutrons is to be calculated for an atom of ${}_{\text{88}}^{\text{226}}\text{Ra}$.

The given symbol of an atom is ${}_{\text{88}}^{\text{226}}\text{Ra}$, so, $\text{Ra}$ represents atomic symbol of radium and $\text{226}$ represents mass number and $\text{88}$ represents the atomic number.

Since,

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

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

So,

The number of protons in the nucleus of an atom of ${}_{\text{88}}^{\text{226}}\text{Ra}$ = 54.

Using, Mass number = Number of neutrons + number of protons, the number of neutrons present in the nucleus of an atom of ${}_{\text{88}}^{\text{226}}\text{Ra}$ can be determined as:

$\begin{array}{l}\text{226 = Number of neutrons + 88}\hfill \\ \text{Number of neutrons = 226 – 88}\hfill \\ \text{Number of neutrons = 138}\hfill \end{array}$

Hence, the correct option is (d) as the number of protons is $\text{88}$ and number of neutrons is $\text{138}$ present in the nucleus of an atom of ${}_{\text{88}}^{\text{226}}\text{Ra}$.