Question

What part of an atom is involved in nuclear reactions?

Answer 1

The nucleus is involved.

Explanation:

There are two types of nuclear reactions, namely nuclear (radioactive) decay and nuclear transmutation.

Radioactive decay is when an unstable nucleus of an atom, generally everything with a higher atomic number than Lead has an unstable nucleus, emits radiation to form a product with a more stable nucleus.

Examples of nuclear decay:

Image from: http://chemwiki.ucdavis.edu/Physical_Chemistry/Nuclear_Chemistry/Nuclear_Reactions

Nuclear transmutation is when a subatomic particle is fired at the nucleus of an atom to change it into a heavier element or to break the nucleus apart to get two nuclei and energy (useful in energy production for electricity).

The two types of nuclear transmutation:

Image from: http://chemistry.tutorvista.com/nuclear-chemistry/nuclear-fission.html

So in both cases it can be seen that the nucleus is involved in nuclear reactions.

Hope I helped :)