Question

In $\alpha $-decay, n/p ratio:
A) May increase or decrease
B) Remains constant
C) Decreases
D) Increases

Answer 1

Hint: The answer is based on the concept of nuclear chemistry where the ratio of number of neutrons to that of number of protons and this value is dependent on the radioactive decay and then writes the change in-decay accordingly.

Complete Solution :
In our classes of chemistry we have studied about the basic topic which deals with nuclear chemistry and also radioactivity of an element.
Now, we shall see what does $\alpha $- decay mean and how the value changes.
- Radioactivity of an element or its isotopes is defined as the phenomenon of emission of particles from the nuclei as a result of nuclear instability.
- There are three most common types of radioactive decay process which include alpha decay, beta decay and gamma decay all of which are indulged in emitting one or more particles or photons.
- $\alpha $- decay is the one in which an atomic nucleus emits an alpha particle (helium nucleus) and thus transforms into a different atomic nucleus.
- The n/p ratio is the ratio of number of neutrons to that of number of protons which is used for successful explanation for predicting stability of the nucleus.
This ratio is close to 1 for the atoms with low atomic numbers and increases steadily with increase in the atomic number.
- For the radioactive decay to take place this ratio is always greater than 1 and therefore with the increase in the n/p ratio, even $\alpha $- decay also increases.
So, the correct answer is “Option D”.

Note: Note that Uranium - 238 is the common element that undergoes an $\alpha $- decay to give thorium – 234 because of the combined extremely high nuclear binding energy and relatively small mass of $\alpha $ particle.