How does an atom enter into the excited state?

An exited atom radiate through the process to gain stability. When the ratio or protons to neutrons is less or higher than that corresponding to the stability ratio the nucleus radiate either:

• beta (-) radiation to reduce the number of neutrons, or
• beta (+) radiation or electron capture to reduce the number of protons
• gamma radiation to bring the nucleus to ground state energy level.

Also an excited atom emits radiation (Alpha, beta, gamma, neutrons, ...) when the nucleus atomic number is higher than 83 to reduce the number of nucleons in the

nucleus to reach stability.