Compléter MagnetismVersion en ligne Complete the text with the words missing par Miguel Domínguez 1 Magnetism arises from two types of motions of electrons in atoms - one is the motion of the in an orbit around the nucleus , similar to the motion of the in our solar system around the sun , and the other is the of the electrons around its axis , analogous to the rotation of the Earth about its own . The orbital and the spin motion independently impart a magnetic on each electron causing each of them to behave as a magnet . The magnetic moment of a magnet is defined by the rotational force by it in a magnetic field of unit strength acting perpendicular to its magnetic axis . In a large fraction of the elements , the magnetic moment of the electrons out because of the Pauli exclusion , which states that each electronic orbit can be occupied by only two electrons of opposite spin . , a number of so - called transition metal atoms , such as iron , cobalt , and , have magnetic moments that are not cancelled ; these elements are , , common examples of magnetic materials . In these transition metal elements the magnetic moment arises only from the spin of the electrons . In the rare earth elements ( that begin with lanthanum in the sixth row of the Table of Elements ) , , the effect of the orbital motion of the electrons is not cancelled , and both spin and orbital motion contribute to the magnetic moment . Examples of some magnetic rare earth elements are : cerium , neodymium , samarium , and europium . In addition to metals and alloys of transition and rare earth elements , magnetic moments are also observed in a wide variety of chemical compounds involving these elements . Among the common magnetic compounds are the metal , which are chemically compositions of metals with oxygen .
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