During alpha decay, what does a nucleus emit?

1. Alpha decay happens when a nucleus has too many protons relative to its neutrons for a stable balance of forces. 2. The nucleus ejects two protons and two neutrons together, which is a helium nucleus. 3. A single electron is emitted during beta decay, not alpha decay. 4. A photon with no mass or charge describes gamma decay, and a single free neutron is not what alpha decay ejects. 5. So two protons and two neutrons as a helium nucleus is correct. _Source: OpenStax Physics (CC BY 4.0), Ch 22 "The Atom", section 22.2 Nuclear Forces and Radioactivity_