Aufbau principle is not satisfied by from Chemistry Structure of

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 Multiple Choice QuestionsMultiple Choice Questions

131.

The basis of quantum mechanical model of an atom is

  • angular momentum of electron

  • quantum numbers

  • dual nature of electron

  • black body radiation


132.

The quantum number which explains the line spectra observed as doublets in case of hydrogen and alkali metals and doublets and triplets in case of alkaline earth metals is

  • spin

  • azimuthal

  • magnetic

  • principal


133.

A compound absorbs light in the wavelength region 490-500 nm. Its complementary colour is

  • red

  • blue

  • orange

  • blue-green


134.

Which of the following sets of quantum numbers is correct for an electron in 3d-orbital?

  • n = 3; l = 2; m = -3; s = +12

  • n = 3; l = 3; m = +3; s = -12

  • n = 3; l = 2; m = -2; s = +12

  • n = 3; l = 2; m = -3; s = -12


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135.

If the kinetic energy of a particle is reduced to half, de-Broglie wavelength becomes

  • 2 times

  • 12 times

  • 4 times

  • 2 times


136.

In an atom the order of increasing energy of electrons with quantum numbers

(i) n=4, l=1      (ii) n=4, l=0     (iii) n=3, l=2 and (iv) n=3, l=1 is

  • III < I <IV < II

  • II < IV < I<III

  • I <III <II <IV

  • IV< II <III <I


137.

The number of angular and radial nodes of 4d orbital respectively are

  • 3,1

  • 1,2

  • 3,0

  • 2,1


138.

The product of uncertainty in velocity and uncertainty in position of a micro particle of mass 'm' is not less than in which of the following?

  • h × 3πm

  • h3π× m

  • h4π × 1m

  • h4π × m


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139.

2p orbitals have

  • n = 1; l = 2

  • n = 1; l = 0

  • n = 2; l = 1

  • n = 2; l = 0


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140.

Aufbau principle is not satisfied by

  • Cr and Cl

  • Cu and Ag

  • Cr and Mg

  • Cu and Na


B.

Cu and Ag

The electrons presents in the different orbitals of the same subshell can exchange their positions. Each such exchange results in release of energy, called exchange energy and hence, leads to a greater stability. As the number of exchanges that can take place is maximum in the exactly half filled and completely filled arrangements, therefore, exchange energy is maximum and hence, the stability is maximum. 

29Cu - 1s2, 2s2 2p6, 3s2 3p6, 4s1, 3d10

47Ag - 1s2, 2s2 2p6, 3s2 3p6, 4s2, 3d10, 4p6 5s1, 4d10

but Aufbau principle states that electrons are filled in increasing order of energy, hence 4s orbital must be filled first than 3d orbital.

In Cu and Ag both electron first enters in the orbital of lower energy, therefore they does not satisfy Aufbau principle.


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