ACS Chemistry Practice Exam 2025 – The All-in-One Guide to Exam Success!

An element is considered paramagnetic if it has unpaired electrons in its atomic or molecular orbitals. The presence of unpaired electrons means that these electrons can align with an external magnetic field, resulting in a net magnetic moment. This characteristic is crucial for paramagnetism, as it distinguishes paramagnetic substances from diamagnetic substances, which have all their electrons paired and do not exhibit any net magnetic moment in the presence of a magnetic field.

In contrast, elements with all paired electrons will exhibit diamagnetism, making them non-magnetic in nature. High electronegativity affects how an atom behaves in chemical bonds but does not directly determine its magnetic properties. Similarly, while filled electron shells are a characteristic of stable electron configurations and may indicate a lack of reactivity, they do not relate to paramagnetism since filled shells often correspond to all electrons being paired. Thus, the key requirement for paramagnetism is indeed the presence of unpaired electrons.