Short Answer Type
Long Answer TypeDiscuss the characteristics of group 13 elements in terms of:
(i) Atomic and ionic radii
(ii) ionisation enthalpy
(iii) Density, melting point and boiling points.
Short Answer TypeLong Answer Type(i) Electronegativity: There is no regular change in electronegativity on moving down the group. Down the group, electronegativity first decreases from B to Al and then increases marginally. This is because of the discrepancies in atomic size of the elements.
(ii) Nature of bonds: According to Fajan’s rule, the smaller the cation, the greater is its tendency to form covalent compounds. Thus, with the increase of M3+ ionic radii down the group from B3+ to Tl3+, the tendency of these ions to form covalent compounds decreases. Thus boron forms mostly covalent compounds while other members form ionic compounds also.
(iii) Oxidation states: The general electronic configuration of group 13 elements [Noble gas] is ns2 np1, so these elements are expected to show a uniform oxidation state of + 3. Boron and aluminium show an oxidation state of +3 only, but gallium, indium and thallium, however, show oxidation states of + 1 and +3.
Explain the following:
(i) Boron is trivalent
(ii) Boron and aluminium tend to form covalent compounds.
Discuss the pattern of variation in the oxidation states of B(Boron) to Tl(Thallium).
Or
What is inert pair effect? Illustrate it with reference to Boron family.
Short Answer TypeStandard electrode potential values 
and that of 
is +1.26 V. Predict about the formation of M3+ ion in solution and compare the electropositive character of the two metals.
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