Class 11 Chemistry - Chapter The p Block Elements NCERT Solutions | Discuss the pattern of variation in the
Discuss the pattern of variation in the oxidation states of
(i) B to Tl and (ii) C to Pb.
(i) B to Tl- they belong to group 13 elements with electronic configuration as ns2 np1. The atoms of these elements have 3 valence electrons, two in s subshell and one in p subshell, therefore all these elements show maximum of + 3 oxidation state. Boron shows only +3 oxidation state in its compound and other elements also show +1 oxidation state. The +1 oxidation state becomes more stable as we move down the group from boron to thallium. The +1 oxidation state is more stable than +3 oxidation state because of inert pair effect .In case of last element, after removal of one electron from p orbital, the remaining ns2 electrons behave like stable noble gases and do not take part in compound formation. This reluctance of the s electron pair to take part in chemical combination is called inert pair effect. The two electrons present in the s-shell are strongly attracted by the nucleus and do not participate in bonding. This inert pair effect becomes more and more prominent on moving down the group. Hence, Ga (+1) is unstable, In (+1) is fairly stable and Tl (+1) is very stable.
|
Group 13 element |
Oxidation state |
|
B |
+3 |
|
Al |
+3 |
|
Ga, In, Tl |
+1, +3 |
The stability of the +3 oxidation state decreases on moving down the group.
(ii) C to Pb- they belongs to group 14 in periodic table and are also called carbon family with electronic configuration of ns2 np2. Therefore, the most common oxidation state exhibited by them should be +4. However, the +2 oxidation state becomes more and more common on moving down the group. C and Si mostly show the +4 oxidation state. On moving down the group, the higher oxidation state becomes less stable. This is because of the inert pair effect. Thus, although Ge, Sn, and Pb show both the +2 and + 4 states, the stability of the lower oxidation state increases and that of the higher oxidation state decreases on moving down the group.
|
Group14 element |
Oxidation state |
|
C |
+4 |
|
Si |
+4 |
|
Ge, Sn, Pb |
+2, +4 |
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