When people consider the magnetic properties of metals, they often think of the strong attraction seen in materials like iron. This leads to a common question about other everyday metals, including zinc. For all practical purposes, pure zinc is not considered magnetic in the way most people understand the term. It will not stick to a refrigerator magnet, nor can it be used to create a permanent magnet. The science behind this non-magnetic behavior reveals its specific classification.
The Direct Answer: Zinc’s Magnetic Classification
While zinc is generally called “non-magnetic,” its true scientific classification is diamagnetic. This term describes a material’s very weak response to an external magnetic field, which is the opposite of attraction. Instead of being pulled toward a magnet, a diamagnetic material like zinc is actually repelled by it. This repulsive force is subtle and usually impossible to notice without highly sensitive laboratory equipment.
Zinc’s interaction with a magnetic field is so slight that it has a small, negative magnetic susceptibility. This negative value confirms the weak repulsion and is the defining characteristic of diamagnetism. The repulsion happens because the external field induces a temporary magnetic moment within the zinc atoms that directly opposes the applied field. This behavior is a consequence of the metal’s internal atomic structure.
Understanding Diamagnetism
The reason zinc is diamagnetic is rooted in the arrangement of its electrons, specifically the phenomenon of electron pairing. Zinc atoms have an electron configuration where all electrons are paired up in their orbitals. This means that both the \(3d\) and \(4s\) subshells are completely filled.
Each electron has a property called spin, which creates a tiny magnetic field known as a magnetic moment. When two electrons occupy the same orbital, they must have opposite spins. Their individual magnetic moments perfectly cancel each other out. Because zinc has no unpaired electrons, the atoms possess no net magnetic moment in their natural state.
When an external magnetic field is applied, it slightly alters the orbital motion of these paired electrons. This change generates a minuscule, induced magnetic field within the zinc metal. This induced field always points in the direction opposite to the external field. This opposition creates the weak repulsive force that defines zinc’s diamagnetic nature.
Comparing Zinc to Everyday Magnets
Zinc’s weak repulsion contrasts sharply with the strong attraction seen in materials used for permanent magnets, which are classified as ferromagnetic. Ferromagnetic materials, such as iron, nickel, and cobalt, are strongly attracted to magnets. They can retain their magnetism after the external field is removed. This powerful magnetism is possible because these elements contain multiple unpaired electrons.
These unpaired electrons allow the atoms to possess a net magnetic moment. In ferromagnetic materials, these moments align into large regions called magnetic domains. When exposed to a magnetic field, these domains align, resulting in a robust attraction.
A third category, paramagnetism, involves materials like aluminum. These materials also have unpaired electrons but are only weakly attracted to a magnet and lose their magnetism instantly. Zinc’s diamagnetism, with its weak repulsion, occupies one end of the magnetic spectrum, while ferromagnetism is at the other.