Chapter 39, Problem 56A

To determine

The reason of the existence of the radioactive elements of atomic number less than the Uranium but the same half-life likes that of elements atomic number greater than the Uranium.

Explanation of Solution

Introduction:

The stability of the radioactive element depends on the composition of the nucleus of the element. If the nucleus is heavy then it try to become stable by radioactive decaying process.

The nucleus of the elements that have greater atomic number than uranium are unstable due to heavy nucleus. So, these elements do not exist in nature.

The nucleus of the element that have lesser atomic number than uranium are stable due to light nucleus and these are formed due to decay of uranium.

Conclusion:

Thus, the elements of smaller atomic number than uranium exist because the nucleus of these elements is lighter than the elements of greater atomic number than uranium.