Multiple Choice QuestionsWhich of the following series of transitions in the spectrum of hydrogen atom fall in visible region?
Balmer series
Paschen series
Brackett series
Lyman series
Assertion (A) : Atoms with completely filled and half-filled sub-shells are stable.
Reason (R): Completely filled and half-filled sub-shells have symmetrical distribution of electrons and have maximum exchange energy.
The correct answer is
(A) and (R) are correct, (R) is the correct explanation of (A)
(A) and (R) are correct, (R) is not the correct explanation of (A)
(A) is correct, but (R)is not correct
(A) is not correct, but (R) is correct
A.
(A) and (R) are correct, (R) is the correct explanation of (A)
The extra stability of half-filled and fully filled electronic configuration can be explained in terms of symmetry and exchange energy. All the orbitals of the same sub-shell are either completely filled or half-filled have more symmetrical distribution of electrons. Consequently, their shielding of one another is relatively small and the electrons are more strongly attracted by the nucleus. This leads to more stability of the atom.
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