The wave numbers of three spectral lines of H atom are considered. Identify the set of spectral lines belonging to Balmer series. (R = Rydberg constant)
- 5R36, 3R16, 21R100
- 7R144, 3R16, 16R255
- 3R4, 3R16, 7R144
- 5R36, 8R9, 15R16
Answer
(1) 5R36, 3R16, 21R100
Solution
For the Balmer series of hydrogen: = R ( 122 - 1n2 ), n = 3, 4, 5, …
n = 3: = R ( 14 - 19 ) = 5R36
n = 4: = R ( 14 - 116 ) = 3R16
n = 5: = R ( 14 - 125 ) = 21R100
These are the three lines of set (1).
(Other sets contain lines of other series, e.g. 3R4, 8R9, 15R16 belong to the Lyman series and 7R144 to the Paschen series.)
Answer: (1)