proton drip line

The proton drip line is a boundary in nuclear physics that marks the limit of how many protons a nucleus can hold before it becomes unstable and spontaneously loses a proton. Beyond this line, adding more protons makes the nucleus unstable, causing it to "drip" protons off. It helps scientists understand which isotopes (varieties of elements with different numbers of protons and neutrons) can exist naturally or be created in laboratories. This concept is important for studying the structure of atomic nuclei, nuclear reactions, and processes in stars.