Platinum (Pt) is a dense, silvery-white metal valued for its resistance to corrosion and high melting point. It is used extensively in fine jewelry, where it is often alloyed for durability. Platinum is also indispensable in industrial applications, particularly in catalytic converters and sensitive electronic components. Understanding how this material interacts with a magnetic field is important.
The Simple Answer: Platinum and Magnets
The practical answer is that pure platinum will not stick to a common refrigerator magnet. If a typical household magnet is held up to a piece of pure platinum jewelry, there will be no noticeable attraction. In everyday terms, this makes platinum effectively non-magnetic, behaving much like gold or silver. Jewelers often use this lack of attraction as a quick test for authenticity. However, the scientific classification of platinum is more complex, as its atoms exhibit a subtle response to an external magnetic field.
The Three Types of Magnetic Behavior
Materials are scientifically categorized into three groups based on how they respond to a magnetic field. Ferromagnetism represents the strongest attraction, seen in metals like iron, nickel, and cobalt. These materials are strongly drawn to a magnet and can retain their own magnetism after the external field is removed.
Diamagnetism is the opposite behavior, where a material is weakly repelled by a magnetic field. This repulsion occurs because the external field changes the orbital motion of the electrons, inducing a magnetic moment that opposes the field. Most materials, including gold and copper, are diamagnetic.
The third category is paramagnetism, which describes a weak, temporary attraction to a magnetic field, a property possessed by pure platinum. This attraction disappears immediately when the external magnetic field is removed. The force is millions of times weaker than ferromagnetic attraction.
Why Platinum is Classified as Paramagnetic
Platinum is classified as paramagnetic due to unpaired electrons within its atomic structure. Each electron acts like a tiny magnet, creating a small magnetic moment. In most materials, electron spins are paired and cancel out, but in platinum, some electrons in the outer 5d orbital shell remain unpaired.
When an external magnetic field is applied, the magnetic moments from these unpaired electrons attempt to align themselves with the field. This momentary alignment causes the weak, paramagnetic attraction. Since the alignment is disorganized among the atoms, the attraction is not strong enough to overcome the material’s weight.
Observing platinum’s paramagnetism requires highly sensitive equipment and powerful electromagnets, making it imperceptible during a simple home test. This non-stick nature is useful in the jewelry trade. If platinum jewelry is strongly attracted to a magnet, it signals that the platinum has been alloyed with a ferromagnetic metal, such as cobalt or iron.