When a radioactive isotope undergoes beta decay, which of the following will not occur?
a. energy is released.
b. the atomic number of the original nucleus changes.
c. the mass number of the original nucleus changes.
d. the original nucleus approaches greater stability.

The correct option is c.

Explanation:

During radioactive decays, large amount of energy is released as the unstable nucleus attains more stability. A beta decay is a radioactive decay in which a positron (beta-positive, ⁰₊₁β) or an electron (beta-minus, ⁰₋₁β) is released. In both cases, the mass number of the original nucleus is not affected but the atomic number is affected as shown below.

An example of a beta-positive decay is

²³⁰₉₁Pa ⇒ ²³⁰₉₀Th + ⁰₊₁β

An example of a beta-minus decay is

³₁H ⇒ ³₂He + ⁰₋₁β

From the above, it can be observed that the mass number does not change.

a) the particles of the chair are strongly held together.