Atomic models and line spectra
| English | 中文 | Pinyin |
|---|---|---|
| energy level/ˈenədʒi ˈlevl/ | 能级 | néng jí |
| emission spectrum/ɪˈmɪʃn ˈspektrəm/ | 发射光谱 | fā shè guāng pǔ |
What would explain this observation?
- An excited gas produces separate coloured lines rather than every wavelength. The pattern is evidence for discrete atomic energy differences.
- Start with a prediction. State the quantities or features you would compare, then decide what evidence could distinguish two explanations.
Build the model
- Atoms have a small positive nucleus and electrons. Emission and absorption spectra arise from transitions between discrete energy levels 能级. A photon energy equals the level difference and obeys E = hf.
- emission spectrum 发射光谱: Wavelength pattern of radiation emitted by a source; energy level: An allowed energy state in a model.
What produces a higher-frequency emitted photon?
An emitted photon corresponds to a transition to a lower energy level. Absorption requires a compatible energy difference. Rutherford scattering supported a small dense nucleus, but that experiment alone did not establish the complete quantum model.
Match each technical term to its precise meaning.
Use the definitions to distinguish related quantities and processes.
Choose evidence that can test it
- An emitted photon corresponds to a transition to a lower energy level. Absorption requires a compatible energy difference. Rutherford scattering supported a small dense nucleus, but that experiment alone did not establish the complete quantum model.
- Read a labelled energy-level diagram before calculating. Keep joules and electronvolts distinct and use the given constants. Compare attributed spectra at a common wavelength scale and avoid looking at unsafe light sources.
Which two habits make the investigation or model in this case more defensible?
Read a labelled energy-level diagram before calculating. Keep joules and electronvolts distinct and use the given constants. Compare attributed spectra at a common wavelength scale and avoid looking at unsafe light sources.
Work from known quantities
- State the known values and their units. Choose the relation because its assumptions fit this case, then rearrange before substitution.
- Known: energy levels are −6.0 and −2.0 eV. A downward transition releases 4.0 eV = 6.4×10⁻¹⁹ J using 1 eV = 1.6×10⁻¹⁹ J. With h = 6.4×10⁻³⁴ J s for this rounded exercise, frequency is 1.0×10¹⁵ Hz.
Levels are −7.0 and −2.0 eV. Find the energy emitted in the downward transition. Use the same sequence: known quantities → model → relation → substitution → unit and interpretation.
Levels are −7.0 and −2.0 eV. Find the energy emitted in the downward transition.
The result is 5 eV. Known: energy levels are −6.0 and −2.0 eV. A downward transition releases 4.0 eV = 6.4×10⁻¹⁹ J using 1 eV = 1.6×10⁻¹⁹ J. With h = 6.4×10⁻³⁴ J s for this rounded exercise, frequency is 1.0×10¹⁵ Hz.
Check the conclusion and its limits
- Negative bound-state energies are relative to a chosen zero; they do not mean a negative photon energy is emitted. A larger downward energy difference gives higher frequency.
- Return to the original observation. Explain what the result supports, which conditions it assumes, and one way to test a competing explanation.
A negative bound-state energy means an emitted photon has negative energy. This claim is false: Negative bound-state energies are relative to a chosen zero; they do not mean a negative photon energy is emitted. A larger downward energy difference gives higher frequency.
Atomic models and line spectra: An emitted photon corresponds to a transition to a lower energy level. Absorption requires a compatible energy difference. Rutherford scattering supported a small dense nucleus, but that experiment alone did not establish the complete quantum model.
A negative bound-state energy means an emitted photon has negative energy.
Negative bound-state energies are relative to a chosen zero; they do not mean a negative photon energy is emitted. A larger downward energy difference gives higher frequency.
Wavelength pattern of radiation emitted by a source: write the technical term.
emission spectrum means Wavelength pattern of radiation emitted by a source.