Therefore, a neutral atom contains the same number of electrons as protons. However, it is possible for an atom to temporarily lose one or more electrons by some means and become an ion . The nucleus is unaffected when an atom is ionized, so it remains the same element. An atom that is unionized is referred to as neutral. An ion can return to being a neutral atom by recombining with enough electrons to equal the number of protons in the nucleus.
Ions are very common in astronomy.
When atoms form molecules, it is the electrons that get together, the nuclei stay distinct. The science of how elements interact with each other is called chemistry . The Earth's environment is particularly good for encouraging atoms to combine to form molecules. In astronomy, on the other hand, it is common to find atoms acting individually, and not in molecules. This individuality makes astronomy simple.