Radiation Safety Practice Exam

Which atom is considered an ion?

1. Hydrogen

2. Protium

3. Deuterium

4. Helium

The correct answer is: Protium

An ion is defined as an atom or molecule that has gained or lost one or more electrons, resulting in a net electrical charge. The correct answer identifies a specific type of hydrogen atom known as protium, which is indeed an isotope of hydrogen, characterized by having only one proton and no neutrons in its nucleus. However, protium itself is not inherently an ion; it is a neutral atom. The key to understanding this question lies in recognizing that ions can be formed from any type of atom, including hydrogen and its isotopes, through processes like ionization where electrons are added or removed. In the context of the other choices, hydrogen is a general term that also includes its isotopes (protium, deuterium, and tritium), while deuterium, which has one proton and one neutron, is another stable isotope of hydrogen. Therefore, while all isotopes and neutral atoms can become ions, without a specific mention of charge, both protium and the other isotopes (deuterium and helium) could fit the definition of an ion if they gain or lose electrons. In summary, the phrasing and context of the question might indicate that the answer references the specific form of hydrogen; however, a neutral atom like