This process is called positron emission or beta plus decay. Here's what happens:

1. A proton in the nucleus decays into a neutron, a positron, and a neutrino.

2. The positron is emitted from the nucleus.

3. The neutrino is also emitted, carrying away some energy and momentum.

The net result is that the atomic number of the nucleus decreases by one (because a proton has turned into a neutron), while the mass number remains the same.

Here's a simplified equation:

p → n + e+ + νe

Where:

* p = proton

* n = neutron

* e+ = positron

* νe = electron neutrino