A radioactive substance contains a number of identical nuclei that emit β-particles. Which property of these nuclei remains unaltered by the emission?

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Question 21

A radioactive substance contains a number of identical nuclei that emit β-particles.

Which property of these nuclei remains unaltered by the emission?

A charge

B neutron number

C nucleon number

D proton number

Reference: Past Exam Paper – June 2015 Paper 12 Q39

Solution:

Answer: C.

Beta particle is ⁰_-1β.

The nucleon number of β-particles is zero. So, the nucleon number of the nucleus formed is the same as the parent nucleus.

Since the β-particle has a negative charge, the daughter nucleus will need to have a charge greater than the parent daughter so that the charge is conserved. Similarly, it will have one more proton than the parent nucleus.

The neutron number will also change as the proton number has changed.

Nucleon number = Neutron number + Proton number