An atom can become magnetic through a process called "paramagnetism" or "ferromagnetism," depending on the specific mechanism involved. Here's a brief explanation of each:
Paramagnetism: Paramagnetic materials are weakly attracted to magnetic fields. In atoms, paramagnetism arises due to the presence of unpaired electrons in their electron configuration. Unpaired electrons have an intrinsic property called "spin" that creates a tiny magnetic field around them. When an external magnetic field is applied, the unpaired electron spins align with the field, resulting in a net magnetic moment for the atom. However, paramagnetic effects are generally weak and temporary since the alignment vanishes when the external magnetic field is removed.
Ferromagnetism: Ferromagnetic materials, such as iron, nickel, and cobalt, can exhibit strong and permanent magnetic properties. Ferromagnetism is a collective effect that arises from the alignment of magnetic moments within a material. In a ferromagnetic substance, groups of atoms called "domains" have their individual magnetic moments aligned in a parallel fashion. The interaction between neighboring domains strengthens this alignment, resulting in a macroscopic magnetization of the material. This alignment can persist even after removing the external magnetic field, making the material magnetized.
It's important to note that the magnetic properties of atoms are primarily determined by their electron configuration and the interactions between the electrons. The specific arrangement and behavior of electrons in an atom or material dictate whether it exhibits paramagnetic or ferromagnetic properties.