Chemistry NCERT Exemplar Solutions Class 11th Chapter Two

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Ans:  option (i) & (iv)

In a multielectron atomic system the energy of an electron depends not only on its principal quantum number (shell), but also on its azimuthal quantum number (subshell). Electrons having the same shells and same subshells have the same energy and they are known as degenerate orbitals.

This is a Multiple Choice Questions as classified in NCERT Exemplar

Ans: option  (iii) & (iv)

The isotopes are defined as atoms with identical atomic numbers but different mass numbers are known as isotopes.

This is a Multiple Choice Questions as classified in NCERT Exemplar

Ans:  option (ii) Alpha particle (He²⁺)

As the wavelength is inversely proportional to the mass of the particles thus the alpha particles would possess the shortest wavelength among the above given option

$\mathit{\lambda }=\frac{\mathit{h}}{\mathit{m}\mathit{v}}$

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Ans: option (iv) The two electrons present in the 2s orbital have spin quantum numbers MS but of opposite sign.

According to Pauli's Exclusion Principle no two electrons should possess the same set of four quantum numbers. Thus the two electrons present in the 2s orbital have spin quantum numbers MS but of opposite sign.

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Ans: option  (ii)

Fe³⁺, Mn²⁺ Fe³⁺ electronic configuration is 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁵ 4s² Mn²⁺electronic configuration is 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁵ 4s

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Ans:  Option (iii) 1:3

The chlorine is a mixture of two isotopes with atomic masses 37U and 35U and its atomic mass is 35.5U. The atomic mass depicts that % composition of Cl-35 is much higher than that of Cl-37 and they are present in the ratio 1:3

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Ans: Option (i)

 “l” which is known as Azimuthal quantum number or orbital angular momentum or subsidiary quantum number depicts the three dimensional shape of the orbital.

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Ans:  option (iii) 9

The total number of orbitals is given by n2, where n is the principal quantum number or the principal shell.

Thus for the third shell number of orbitals is 32 i.e. 9

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Ans: (ii) Heisenberg's uncertainty principle.

According to Heisenberg's uncertainty principle it is impossible to determine simultaneously, the exact position and exact momentum (or velocity) of an electron. Thus it implies that determining the trajectory of an electron is impossible as it requires exact position and velocity which is not possible as per the uncertainty principle.

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Ans: option (iii) 2

The number of angular nodes is given by n-l

where n is principal quantum number, l is azimuthal quantum number

For 4d orbital, n=4 and l=2

Thus, the number of angular nodes

 = n-l

 = 4-2

 = 2