* Nucleons are the particles that make up the nucleus of an atom: protons and neutrons.

* Beta decay is the process where a neutron in the nucleus decays into a proton, an electron (the beta particle), and an antineutrino.

Here's the breakdown:

1. Before decay: You have a neutron (1 nucleon) in the nucleus.

2. During decay: The neutron transforms into a proton (1 nucleon), an electron (not a nucleon), and an antineutrino (not a nucleon).

3. After decay: The nucleus now has one fewer neutron but one more proton, maintaining the same total number of nucleons.

In summary: While the number of protons and neutrons changes, the total number of nucleons (protons + neutrons) remains constant during beta decay.