In hydrogen's emission spectrum, the Balmer series corresponds to transitions to which energy level, and where do the emitted lines appear?

• A. Transitions to n = 1 from higher n; lines in the ultraviolet region.
• B. Transitions to n = 2 from higher n; lines appear in the visible region.
• C. Transitions from n = 2 to n = 3; infrared lines.
• D. Emission from the ground state only; no lines.

Answer: (B)

Balmer series involves transitions to the second energy level, n = 2, from higher levels (n = 3, 4, 5, …). When the electron drops to n = 2, the energy released as a photon falls in the visible portion of the spectrum, which is why these lines are seen with the naked eye in hydrogen discharge spectra. Examples include the 3→2 transition giving the red H-alpha line around 656 nm, the 4→2 line around 486 nm, the 5→2 line around 434 nm, and the 6→2 line around 410 nm. Transitions to n = 1 (Lyman) produce ultraviolet light, while transitions to n = 3 (Paschen) produce infrared light.