When two protons undergo a nuclear reaction, they change into:

* One neutron

* One positron (a positively charged anti-electron)

* One neutrino

This process is called positron emission or beta-plus decay. It's one of the ways that radioactive isotopes can decay.

Here's a simplified equation representing the process:

p + p → n + e⁺ + νₑ

where:

* p represents a proton

* n represents a neutron

* e⁺ represents a positron

* νₑ represents an electron neutrino