Ions Undisturbed atoms are electrically neutral; the number of electrons is the same as the number of protons. An atom that has electric charge is called an ion. It might acquire this charge by losing electrons--in which case the charge is positive--or by picking up some extra ones, making the charge negative. The process of making an atom into an ion is called ionization--hence the term "ionization energy." Ions are formed in many chemical reactions. Ionization can also be caused by radiation, such as high-energy photons or charged particles. The key is to hit the atoms with enough energy to shuffle electrons around.

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