why is calcium listed as paramagnetic even though it has no unpaired electron ??
Now from electronic configuration its is seen that all electron are paired up i.e Ca should be diamagnetic. The magnetic factor not only depends on the electronic configuration but also depends on the vacant orbital that are present next to valence orbital. Now Ca contain an empty d orbital whose energy is very close to valence s orbital. This presence of low lying vacant orbital near electrons of 4s orbital sometime cause transition of electron of 4s and introduce the paramagnetic character by creating an unpaired electron in s orbital and vacant d orbital. This process occur due to less energy difference outer s and d orbital.
Secondly, due to above process their occur delocalization of electron as electron tends to go to d orbital and come back to s orbital again and again . This allow Ca to have some amount of net paramagnetic character.
But mostly Ca in its ground state is diamagnetic.