solution-
(a)Ferromagnetism-
A substance which exhibits unusually large para-magnetism and shows permanent magnetism even in absence of magnetic field is called Ferromagnetism substance.
Examples are Fe ,Ni,Co,Cro2,Fe3O4 and alnico(alloy of Al,Ni,Co,Fe and Cu).
A Ferromagnetic Substance if magnetised once remains permanently Magnetised.
Ferromagnetism occurs duo to spontaneous alignment of Magnetic Moments(duo to unpaired electrons)in the same direction, as shown in figure given below:
↑↑↑↑↑↑↑↑↑↑↑↑↑↑(feromagnetism)
(b)paramagnetism
A substance which is attracted by a magnetic field is called paramagnetismsubstance.
Examples are O2 ,Cu^2+,Fe^3+.
paramagnetism is caused by the presence of permanent magnetic dipoles due to unpaired electrons in the atoms, ions or molecules.However,paramagnetic substances lose their magnetic character in the absence of magnetic field.
(c)ferrimagnetism
A Substance which exhibits fairly good paramagnetic character is called ferrimagnetism substance.
Examples are Fe3O4,ferrites having the formula M^2+Fe2O4(where M^2+ =Mg^2+Cu^2+ or Zn^2+)
↑↑↓↑↑↓↑↑↓↑↑↓(ferrimagnetism)
In ferrimagnetism substances,the alignment of magnetic moments in opposite directions are not Equal.As a result,the substance has net magnetic moment.
Fe3O4(ferrimagnetic substance) on heating to 850 k becomes paramagnetic because at this temperature,there is greater alignment of spins in one direction.
(d)antiferromagnetism
Substances which are expected to posses paramagnetism or ferromagnetism on the basis of unpaired electrons,but actually they posses zero net magnetic moment are called anti-ferromagnetic substances, e.g MnO.Antiferromagnetism is due to the presence of equal number of magnetic moments in the opposite directions as shown in figure given below.
↑↓↑↓↑↓↑↓(anti-ferromagnetism)
(v)12-16 and 13-15 group compounds-
The solid binary compounds prepared by combining elements of group 13 and 15 or group 12 and 16 are classified as:
(i)12-16 compounds:Zns,Cds,Cdse,HgTe having sufficient ionic nature.
(ii)13-15 Compounds: AlP,GaAs,InSb have large covalent nature Both (i) and (ii)compounds have interesting electrical and optical properties.The compounds are Semi-conductors
