Gurmeet Singh posted an Question
January 25, 2021 • 22:30 pm 30 points
  • IIT JAM
  • Geology (GG)

0 the change in coordination number of silicon (si) when o-quartz transforms to stishovite, which has octahedral coordination, is (b) 4 (a) 2 (c) 6 (d) 8

0 The change in coordination number of silicon (Si) when o-quartz transforms to stishovite, which has octahedral coordination, is (B) 4 (A) 2 (C) 6 (D) 8

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    Saurabh 1

    Correct answer would be 2... As the coordination number of stishovite is 6 while that of alpha quartz(or other quartz polymorph) is 4. So difference (6-4=2) ...

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    Sajan sarthak Best Answer

    The coordination number of stishovite is 6, so the silicon atoms are all surrounded by 6 oxygen atoms. The crystal structure of stishovite does not fit in the classification scheme of silicates, so stishovite could well be considered a non-silicate. Stishovite and coesite are both not stable at normal pressures and normal temperatures, but since their transitions into a low pressure silica polymorphs are reconstructive phase transitions that involve a complete rearrangement of the atoms in the crystal lattice, both are metastable at normal conditions. Coordination no of Alpha quartz is 4 so Difference is 6-4 = 2

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