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NCERT Class XII Chemistry
Chapter - The p-Block Elements
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Question : 38 of 74
Marks: +1, -0
Give the formula and describe the structure of a noble gas species which is isostructural with:
(i) ICl4−\mathrm{ICl}^{-}_{4}
(ii) IBr2−\mathrm{IBr}^{-}_{2}
(iii) BrO3−\mathrm{BrO}^{-}_{3}
Solution:  
(i) Structure of ICl4−\mathrm{ICl}^{-}_{4} : I in ICl4−\mathrm{I} \text{ in } \mathrm{ICl}^{-}_{4} has four bond pairs and two lonepairs. Therefore, according to VSEPR theory, it should be square planaras shown.
Here, ICl4−\mathrm{ICl}^{-}_{4} has (7 + 4 × 7 + 1) = 36 valence electrons. A noblegas specieshaving 36 valence electrons is
XeF4_{4}(8 + 4 × 7 = 36). Therefore, like ICl4−\mathrm{ICl}^{-}_{4} , XeF4_{4} is also square planar.
(ii) Structure of IBr2−\mathrm{IBr}^{-}_{2} :I\mathrm{I} in IBr2−\mathrm{IBr}^{-}_{2} has two bond pairs and three lone pairs.So,according to VSEPR theory, it should be linear.Here,IBr2−\mathrm{IBr}^{-}_{2} has 22 (7 + 2 × 7 + 1) valence electrons.A noble gas species having 22 valence electrons is XeF2_{2} (8 + 2 × 7 = 22).Thus, like IBr2−\mathrm{IBr}^{-}_{2} , XeF2_{2} is also linear :
(iii)Structure of BrO3−\mathrm{BrO}^{-}_{3}: The central atom Br has seven electrons. Four ofthese electrons form two double bonds or coordinate bonds with twooxygen atoms while the fifth electron forms a singlebond with O−^{-}ion.The remaining two electrons form one lone pair. Hence, in all there arethree bond pairs and one lone pair around Br atom in BrO3−\mathrm{BrO}^{-}_{3}. Therefore,according to VSEPR theory, BrO3−\mathrm{BrO}^{-}_{3}should be pyramidal.
Here,BrO3−\mathrm{BrO}^{-}_{3}has26(7 + 3 × 6 + 1 = 26) valence electrons. A noble gas specieshaving 26 valence electrons is XeO3\mathrm{XeO}_{3}(8 + 3 × 6 = 26). Thus, like BrO3−\mathrm{BrO}^{-}_{3} , XeO3\mathrm{XeO}_{3}is also pyramidal.
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