Atomic models and line spectra
Đã giới thiệu| English | Ý nghĩa |
|---|---|
| energy level/ˈenədʒi ˈlevl/ | mức năng lượng |
| emission spectrum/ɪˈmɪʃn ˈspektrəm/ | quang phổ phát xạ |
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.
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?
Độ khó 1/5 · 100 xu + một phần thưởng nhỏ cho lần hoàn thành đầu tiên trong ngày
Emitted photon energy equals the difference between the levels, and E = hf ties frequency to that difference. A larger downward jump emits a higher-frequency photon; upward transitions require absorption, and h is a universal constant.
Match each technical term to its precise meaning.
Độ khó 2/5 · 140 xu + một phần thưởng nhỏ cho lần hoàn thành đầu tiên trong ngày
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.
In the lab: 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?
Độ khó 2/5 · 140 xu + một phần thưởng nhỏ cho lần hoàn thành đầu tiên trong ngày
Stating the conditions and assumptions lets others repeat the work exactly, and recording the supporting evidence lets them check the conclusion. Hiding disagreeing results removes the evidence that could challenge a wrong conclusion, and one measurement can never establish a wider claim.
Work from known quantities
- 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.
Your turn: Levels are −7.0 and −2.0 eV. Find the energy emitted in the downward transition.
Levels are −7.0 and −2.0 eV. Find the energy emitted in the downward transition.
Độ khó 2/5 · 140 xu + một phần thưởng nhỏ cho lần hoàn thành đầu tiên trong ngày
The result is 5 eV. Known: levels -7.0 and -2.0 eV; downward transition. Photon energy = level difference = (-2.0) - (-7.0) = 5.0 eV. The energies are negative relative to the ionization zero, but the emitted photon carries the positive difference.
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.
Not true: A negative bound-state energy means an emitted photon has negative energy. Level energies are measured relative to a chosen zero (a free electron at rest), so bound states are negative. The photon energy is the positive DIFFERENCE between levels - differences of negative numbers are positive.
- Atoms have a small positive nucleus and electrons.
- An emitted photon corresponds to a transition to a lower energy level.
- Watch for: negative bound-state energies are relative to a chosen zero; they do not mean a negative photon energy is emitted.
Write from a photon energy of 8 electronvolts
- Levels are minus 12.0 and minus 4.0 electronvolts.
- Find the photon energy of the downward transition. A negative level does not make the photon energy negative.
A negative bound-state energy means an emitted photon has negative energy.
Độ khó 1/5 · 100 xu + một phần thưởng nhỏ cho lần hoàn thành đầu tiên trong ngày
Level energies are measured relative to a chosen zero (a free electron at rest), so bound states are negative. The photon energy is the positive DIFFERENCE between levels - differences of negative numbers are positive.
Wavelength pattern of radiation emitted by a source: write the technical term.
Độ khó 1/5 · 100 xu + một phần thưởng nhỏ cho lần hoàn thành đầu tiên trong ngày
emission spectrum means Wavelength pattern of radiation emitted by a source.
Energy levels are minus 12.0 and minus 4.0 electronvolts. What photon energy is emitted in the downward transition, and why is that energy not negative?
The emitted photon energy is the drop between the two levels.
What is the emitted photon energy?
Độ khó 1/5 · 100 xu + một phần thưởng nhỏ cho lần hoàn thành đầu tiên trong ngày
The levels differ by 8 electronvolts, and the photon energy is that positive difference.