Chemistry · Bohr model of a hydrogen atom: its postulates, derivation of the relations for the energy of the electron and radii of the different orbits, limitations of Bohr's model

How many lines in the spectrum will be observed when electrons return from 7 th

How many lines in the spectrum will be observed when electrons return from 7 th shell to 2nd shell?

  • A. 13
  • B. 14
  • C. 15
  • D. 16

Step-by-step solution

The number of spectral lines when an electron transitions from a higher shell (n=7) to a lower shell (m=2) is given by the formula (n-m+1)(n-m)/2 = (7-2+1)(7-2)/2 = (6×5)/2 = 15. This counts all possible transitions between any two energy levels from 7 down to 2, including direct and indirect jumps.
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