Which of the following compounds is metallic and ferromagnetic?

CsCl crystallises in body centred cubic lattice. If 'a' its edge length, then which of the following expression is correct?

  • straight r subscript Cs to the power of plus space plus straight r subscript Cl to the power of minus end subscript space equals space 3 straight a
  • straight r subscript Cs to the power of plus space plus straight r subscript Cl to the power of minus end subscript space equals space fraction numerator 3 straight a over denominator 2 end fraction
  • straight r subscript Cs to the power of plus space plus straight r subscript Cl to the power of minus end subscript space equals space fraction numerator square root of 3 over denominator 2 end fraction straight a
  • straight r subscript Cs to the power of plus space plus straight r subscript Cl to the power of minus end subscript space equals space fraction numerator square root of 3 over denominator 2 end fraction straight a

C.

straight r subscript Cs to the power of plus space plus straight r subscript Cl to the power of minus end subscript space equals space fraction numerator square root of 3 over denominator 2 end fraction straight a

In CsCl, Cl- lie at corners of simple cube and Cs+ at the body centre, Hence, along the body diagonal, Cs+ and Cl- touch each other so

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Sodium metal crystallises in a body centred cubic lattice with a unit cell edge of 4.29 Å The radius of sodium atom is approximate:

  • 1.86 Å

  • 3.22Å

  • 5.72 Å

  • 5.72 Å


A.

1.86 Å

According to the figure

(AC)2 = (AB)2 + (BC)2
(AC)2 = a2 + a2 = 2a2
(AD)2 = (AC)2+ (DC)2
(4r)2 = 2a2 + a2

16r2 = 3a2

Now, When Na metal crystallises in bcc unit cell with unit cell edge,
a = 4.29Å 
We have the formula for radius,
i.e,  =1.86Å 
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Lithium forms body centred cubic structure. The length of the side of its unit cell is 351 pm. Atomic radius of the lithium will be

  • 75 pm

  • 300 pm

  • 240 pm

  • 240 pm


D.

240 pm

In body centred cubic structure,
Edge length = a = 351 pm, radius= r=?

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Which of the following compounds is metallic and ferromagnetic?

  • VO2

  • MnO2

  • TiO2

  • TiO2


D.

TiO2

Only three elements iron (Fe) cobalt (Co) and Nickel (Ni) show ferromagnetism at room temperature. CrO2 is also a metallic and ferromagnetic compound which  is used to make magnetic tapes for cassette recorders

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In a face centred cubic lattice, atom A occupies the corner positions and atom B occupies the face centre positions. If one atom of B is missing from one of the face centred points, the formula of the compound is:

  • A2

  • AB2

  • A2B3

  • A2B3


D.

A2B3

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