Which of these conditions most likely produces an unstable isotope?
a. equal numbers of protons and neutrons in a small nucleus
b. equal numbers of protons and neutrons in a large nucleus more neutrons than protons in a nucleus more electrons than protons in an atom

b.equal numbers of protons and neutrons in a large nucleus more neutrons than protons in a nucleus more electrons than protons in an atom

The correct option is b.equal numbers of protons and neutrons in a large nucleus more neutrons than protons in a nucleus more electrons than protons in an atom.

Explanation:

Each chemical element is characterized by the number of protons in its nucleus, which is called the atomic number Z. But in the nucleus of each element it is also possible to find neutrons, the number of which can vary. The atomic mass (A) is obtained by adding the number of protons and neutrons of a given nucleus.

The same chemical element may consist of different atoms, that is, their atomic numbers are the same, but the number of neutrons is different. These atoms are called element isotopes.

The stability of an isotope depends on the ratio between its number of protons and neutrons.

Usually, what makes an isotope unstable is the large nucleus. If a nucleus becomes large enough from the amount of neutrons, it will be unstable and attempt to expel its neutrons and / or protons to achieve stability. That is, energy and particles are emitted when it changes from this unstable to a more stable one. The emission of neutrons / protons is called radioactivity.

In summary, for an isotope to be radioactive, it must exhibit a proportion between its amount of neutrons and protons that is not adequate to maintain the stability of the nucleus.

Then, the correct option is b.equal numbers of protons and neutrons in a large nucleus more neutrons than protons in a nucleus more electrons than protons in an atom.