What is the Balmer series in hydrogen and what does it reveal about hydrogen's electron energy levels?

• A. Transitions to n=1; ultraviolet lines.
• B. Transitions to n=3; infrared lines.
• C. Transitions to n=2; visible spectral lines reveal discrete energy levels in hydrogen.
• D. Emit gamma radiation.

Answer: (C)

The Balmer series shows that hydrogen’s electron energy levels are quantized and that specific energy gaps produce photons with particular energies. It consists of transitions where the electron drops to the second energy level (n = 2) from higher levels (n ≥ 3). Each drop emits a photon whose energy corresponds to the difference between the initial level and n = 2, and these photons fall in the visible part of the spectrum, giving the familiar visible lines of hydrogen. This visible set of lines confirms that only certain energy differences occur in hydrogen, rather than a continuous range. If the electron were to drop to n = 1, the lines would be ultraviolet (Lyman series); to n = 3, infrared; and so on. So, the Balmer series reveals discrete energy levels in hydrogen and that visible spectral lines arise from transitions to the n = 2 level.