Which property makes certain metals paramagnetic?

The property that makes certain metals paramagnetic is unpaired electrons. In the context of magnetism, materials are categorized based on their electron configurations. Paramagnetic materials have one or more unpaired electrons in their atomic or molecular structure. These unpaired electrons generate a net magnetic moment, which allows the material to be attracted to an external magnetic field.

When a magnetic field is applied, the unpaired electrons align with the field, resulting in the material exhibiting magnetic properties. However, this effect diminishes when the external magnetic field is removed, as the thermal agitation at higher temperatures disrupts the alignment of the unpaired electrons.

In contrast, metals that have all their electrons paired are generally not magnetic, as the magnetic moments cancel out. This distinction highlights the importance of electron configuration in determining the magnetic properties of materials. Other characteristics like ductility, electrical conductivity, and density do not play a role in a metal's paramagnetism.