ACS Chemistry Practice Exam 2026 – The All-in-One Guide to Exam Success!

When an element has low ionization energy, it means that it requires relatively little energy to remove an electron from an atom in its gaseous state. This characteristic indicates that the element can easily lose electrons, which is typically a property of metals. Metals tend to have low ionization energies because their outermost electrons are not held tightly by the nucleus, allowing them to be removed more easily. As a result, these elements can readily participate in chemical reactions, often forming cations by losing one or more electrons.

In contrast, elements with high ionization energies are more likely to hold onto their electrons, suggesting a tendency to gain electrons rather than lose them. The other choices refer to different behaviors or properties of elements that do not correlate directly with low ionization energy; for example, easily gaining electrons relates more to nonmetals and their affinities, while electronegativity concerns an atom's ability to attract electrons in chemical bonds, both of which are not indicative of low ionization energy.