Cobalt is a chemical element that is part of the transition metals group in the periodic table. It has an atomic structure with 27 protons and electrons and 32 neutrons. Cobalt is a hard and brittle metal that can be magnetized. It is often used in alloys with other metals to make them stronger and more resistant to corrosion. Cobalt is also an important component in rechargeable batteries, as well as in jet engine parts and prosthetic devices.