Multiple Choice Questions

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In a transition series, with increase in atomic-number, the paramagnetism

  • increases gradually

  • decreases gradually

  • first increases to a maximum and then decreases

  • first decreases to a minimum and then increases


C.

first increases to a maximum and then decreases

The paramagnetism of transition elements of a given series increases on moving left to rght in a period and attain a maximum value and after that, it goes on decreasing towards the end of period. This is due to the fact that the magnetic moment or paramagnetism is directly related to the number of half-filled d-orbitals. In the beginning, the number of unpaired electrons in d-orb1tals increases till the middle of the period (d1 to d5). After this, the pairing of electrons occurs in d-orbitals (d6 to d10).

Thus, in a given transition senes, with increases in atomic-number, the paramagnetism first increases
to a maximum and then decreases.


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Which one of the following shows highest magnetic moment?

  • Fe2+

  • Co2+

  • Cr3+

  • Ni2+


Which of the following has the maximum number of unpaired 'd' electrons?

  • Zn2+

  • Fe2+

  • Ni3+

  • Cu+


The electronic configuration of Cu2+ ion is

  • [Ar] 3d8 4s1

  • [Ar] 3d9 4s0

  • [Ar] 3d7 4s2

  • [Ar] 3d8 4s0


The spin only magnetic moment of Mn4+ ion is nearly

  • 3BM

  • 6BM

  • 4BM

  • 5BM


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Mercury is a liquid metal because

  • it has a completely filled s orbital

  • it has a small atomic size

  • it has a completely filled d orbital that prevents d-d overlapping of orbitals

  • it has a completely filled d orbital that causes d-d overlapping


In chromite ore, the oxidation number of iron, and chromium are respectively

  • +3,+2

  • +3,+6

  • +2,+6

  • +2,+3


In chromite ore, the oxidation number of iron and chromium are respectively

  • +3, +2

  • +3, +6

  • +2, +6

  • +2, +3


An element with atomic number 21 is a

  • halogen

  • representative element

  • transition element

  • alkali metal


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Which of the following is a negatively charged bidentate ligand?

  • Cyano

  • Ethylene diamine

  • Acetato

  • Dimethyl glyoximato


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