2.15 Make an argument for why spectra are direct evidence for the existence of quantized energy levels in an atom.

Why are spectra direct evidence for the existence of quantized energy levels in an atom? (Claim)

Claim: Spectra provide direct evidence for the existence of quantized energy levels in atoms because the light emitted or absorbed by atoms occurs at specific, discrete wavelengths.

Why are spectra direct evidence for the existence of quantized energy levels in an atom? (Evidence)

Evidence:

• When atoms absorb or emit light, they only do so at certain wavelengths, corresponding to specific energy transitions between quantized energy levels in the atom.

• The discrete lines observed in the atomic emission and absorption spectra (such as those in hydrogen’s Balmer series) can only be explained if the energy levels within the atom are quantized, meaning the energy values are restricted to certain fixed levels.

Why are spectra direct evidence for the existence of quantized energy levels in an atom? (Reasonong)

Reasoning:

• If energy were continuous, light could be emitted or absorbed at any wavelength, leading to a continuous spectrum. However, the observed line spectra indicate that only specific amounts of energy are released or absorbed during electron transitions, supporting the idea that the electron energy levels in atoms are quantized.

• Therefore, the existence of these distinct spectral lines proves that atomic energy levels are discrete rather than continuous.

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