Q.a) Every substance has some magnetic properties associated with it. How will you account for the following magnetic properties?
i) Paramagnetic property.

Magnetic behaviour depends on unpaired electrons and domain alignment; the compound's formula follows from counting hcp lattice points versus tetrahedral voids.

a) Origin of magnetic properties

i) Paramagnetic property: A substance is paramagnetic if its atoms/ions/molecules contain one or more unpaired electrons. Each unpaired electron behaves as a tiny magnetic dipole (due to its spin and orbital motion). In the absence of a field these dipoles are randomly oriented, so there is no net magnetism, but when placed in an external magnetic field the dipoles align with the field, so the substance is weakly attracted into the field. This property is lost once the field is removed (e.g. O2, Cu2+, Fe3+).

ii) Ferromagnetic property: In a ferromagnetic substance the metal ions are grouped into small regions called domains, each domain acting as a tiny magnet. In the unmagnetised state these domains are randomly oriented so their magnetic moments cancel. On applying an external magnetic field, all the domains get oriented in the direction of the field, and this alignment is so strong that it persists even after the field is removed — giving strong permanent magnetism (e.g. Fe, Co, Ni, CrO2).

b) Formula of the compound

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