Match the following :

	List-1  (Magnetic property)		List-2  (Substance)
a)	ferromagnetic	1)	${\mathrm{O}}_2$
b)	anti ferromagnetic	2)	${\mathrm{CrO}}_2$
c)	ferrimagnetic	3)	MnO
d)	paramagnetic	4)	${\mathrm{Fe}}_3{\mathrm{O}}_4$
		5)	${\mathrm{C}}_6{\mathrm{H}}_6$

The correct answer is

C₆H₆ is a diamagnetic substance, as it is weakly repelled by a magnetic field.
CrO₂ is a ferromagnetic substance, which is attracted very strongly by a magnetic field.
MnO is an antiferromagnetic substance as its domains cancel out each other’s magnetic moment.
Fe₃O₄ (magnetite) is a ferrimagnetic substance because in it the magnetic moments of the domains are aligned in parallel and anti-parallel direction in unequal number.

Oxygen molecule has two unpaired electrons.Electrons not only go around the atom in their orbitals, they also spin, which creates a magnetic field. Unpaired electrons spin in the same direction as each other, which increases the magnetic field effect. Hence, it is paramagnetic.