Question

Explain the following with suitable examples:

(i) Ferromagnetism 

(ii) Paramagnetism 

(iii) Ferrimagnetism 

(iv) Antiferromagnetism 

(v) 12 -16 and 13- 15 group compounds.

Answer 1

(i) Ferromagnetism is considered as an extreme case of paramagnetism. Those substances with a strong attraction to an external magnetic field and those retain a permanent magnetism even when the field is removed are known as ferromagnetic substances. Ferrimagnetism is caused by spontaneous alignment of magnetic moment of atoms or ions in the same direction. Examples of ferromagnetic substances are Fe, CO, Ni, CrO₂ alloys of Fe, CO and Ni etc. Once such a material is, magnetised, it remains permanently magnetised Ferromagnetic

 

(ii) Paramagnetic substances are those which are attracted by magnetic field and have impaired electrons. They lose magnetism in the absence of magnetic field. The greater the number of unpaired electrons, the greater the magnetic moment of the substance and hence greater the paramagnetism. E.g.: O₂, CuO, Fe³⁺, Al, Mn, Cu²⁺ etc. 

(iii) These are substances which are expected to have large magnetism on the basis of unpaired electrons but actually have small net magnetic moment. This is due to the alignment of magnetic moment in opposite direction in unequal numbers resulting in a net magnetic moment.

(iv) These are substances which are expected to possess paramagnetism or ferromagnetism on the basis of unpaired electrons but they actually possess zero net magnetic moment. It arises due to the alignment of magnetic moments in opposite direction in a compensatory manner resulting a zero magnetic moment.

(v) Germanium and silicon are group 14 elements and have a characteristic valance of four and form four bonds as in diamond. A large variety of solid state materials have been prepared by combination of groups 13 and 15 or 12 and 16 to stimulate average valence of four as Ge or Si. Typical compounds of group 13 -15 are InSb, A1P and GaAs. Gallium arsenide (GaAs) semiconductors have very fast response and have revelutionised semi – conductor devices. ZnS, CdS, CdSe and HgTe are examples of group 12 -16 compounds. In these compounds, the bonds are not perfectly covalent and the ionic character depends on the electronegativities of the two elements.