Which materials are classified as paramagnetic?

Paramagnetic materials are those that have a small, positive susceptibility to magnetic fields, meaning they are attracted to magnets. This behavior arises because these materials have unpaired electrons in their atomic structure, which contribute to a net magnetic moment.

Platinum and chromium, as identified in the correct answer, both exhibit paramagnetic properties. Platinum, despite being primarily known for its noble characteristics, has unpaired electrons that allow it to respond weakly to magnetic fields. Chromium, on the other hand, is also known for its unpaired electrons resulting in it being paramagnetic.

In contrast, other materials mentioned in the incorrect options have different magnetic properties. For example, copper and brass are considered diamagnetic and do not possess unpaired electrons, resulting in very weak repulsion from magnetic fields. Iron and nickel are considered ferromagnetic, which means they have strong magnetic properties and can be permanently magnetized. Cobalt also falls under ferromagnetic; while aluminum has some paramagnetic characteristics, it is not as pronounced as the characteristics of chromium and platinum. Therefore, the focus should remain on the atomic structure and electron configurations to identify paramagnetism.