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NCERT Class XII Chemistry
NCERT Class XII Chemistry
Chapter - The p-Block Elements
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Question : 38 of 74
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Give the formula and describe the structure of a noble gas species which is isostructural with: (i) (ii) (iii)
Solution:
(i) Structure of : has four bond pairs and two lonepairs. Therefore, according to VSEPR theory, it should be square planaras shown.Here, has (7 + 4 × 7 + 1) = 36 valence electrons. A noblegas specieshaving 36 valence electrons isXeF(8 + 4 × 7 = 36). Therefore, like , XeF is also square planar.(ii) Structure of : in has two bond pairs and three lone pairs.So,according to VSEPR theory, it should be linear.Here, has 22 (7 + 2 × 7 + 1) valence electrons.A noble gas species having 22 valence electrons is XeF (8 + 2 × 7 = 22).Thus, like , XeF is also linear :
(iii)Structure of : 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 Oion.The remaining two electrons form one lone pair. Hence, in all there arethree bond pairs and one lone pair around Br atom in . Therefore,according to VSEPR theory, should be pyramidal.Here,has26(7 + 3 × 6 + 1 = 26) valence electrons. A noble gas specieshaving 26 valence electrons is (8 + 3 × 6 = 26). Thus, like , is also pyramidal.

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