Chapter 4.4, Problem 28SSC

Interpretation Introduction

Interpretation:  Difference of mass of an alpha particle and an electron needs to be explained.

Concept introduction:  An alpha particle contains two protons and two neutrons. It carries a charge of +2. It is helium atom with no electrons.

An electron is a subatomic particle that has a negative charge and moves freely in an atom.

Answer to Problem 28SSC

An alpha particle is $6.68\times {10}^{-27}kg$ times heavier than an electron.

Explanation of Solution

The mass of all the subatomic particles is as follows:

Mass of an electron $=9.11\times {10}^{-31}kg$

Mass of proton is $1.67\times {10}^{-27}kg$

Mass of neutron is $1.67\times {10}^{-27}kg$

Now, in alpha particle there are 2 protons, 2 neutrons and zero electrons. Thus, total mass of an alpha particle can be calculated as follows:

$m=2\left(1.67\times {10}^{-27}\right)+2\left(1.67\times {10}^{-27}\right)=6.68\times {10}^{-27}\text{ kg}$

Mass of an alpha particle $=6.68\times {10}^{-27}kg$

Difference $=6.68\times {10}^{-27}kg-9.11\times {10}^{-31}kg\approx 6.68\times {10}^{-27}kg$

Conclusion

Hence, an alpha particle is $6.68\times {10}^{-27}kg$ times heavier than an electron.