A substance is said to posess paramagnetic character if it has one ore more unpaired electrons, however if all the electrons are paired it should be diamagnetic. Taking this concept to Magnessium (Mg) it should be obvious to tell that Magnessium is diamagnetic (since all its electrons are paired) however Mg is practically found to be Paramagnetic. there are many other such examples. could anyone help in this regard?

In paramagnetic materials, such as aluminum, magnesium, and platinum, the atoms have permanent magnetic moments, but do not form domains. An external magnetic field tends to line the atoms up parallel to the external field, but the effect is much smaller and is proportional to the external field, so when the external field is removed, the atoms point randomly and no permanent effect remains.
in short we can say that above element have weak form of magnetism known as paulis magnetism and they have low magnetc suseptibilty