The Solid State

  • Question 37

    How many atoms can be assigned to its unit cell if an element forms (i) a body centred cubic cell and (ii) a face centred cubic cell?

    (i) for a body centred cubic cell 2 atoms.        
    (ii)for  face centred cubic cell 4 atoms.
    Question 38

    How many Ca+ ions occupy second nearest neighbour locations to a central Cs+ ion in caesium chloride crystal?

    Co-ordination number of Cs+ ion is 8 in the crystal of caesium chloride .
    Question 39

    How many Na+ ions occupy second nearest neighbour locations of a Na+ ion in the structure of sodium chloride crystals?

     The second nearest Co-ordination number of Na+ ions is 12.
    Question 40

    Why FeO is non-stoichiometric with the formula Fe0.95 O explain?

    The non-stoichiometry reflect the ease of oxidation of Fe2+ to Fe3+ effectively replacing a small portion of Fe2+ with two thirds their number of Fe3+. Thus for every three 'missing' Fe2+ ions, the crystal contains two Fe3+ ions to balance the charge .   i.e. 3Fe2+ = 2Fe3+ to maintain electrical neutrality

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