Atomic changes produce photons
Photon
A discrete packet of electromagnetic energy.
- Electrons in atoms occupy discrete energy levels.
- When an electron moves to a lower energy level, the atom emits a photon whose energy equals the difference between the two levels.
- An atom absorbs a photon only when its energy matches an allowed energy-level difference.
- Different atomic energy gaps can produce infrared, visible or ultraviolet radiation.
Nuclear changes produce gamma rays
Gamma radiation
Gamma radiation is electromagnetic radiation emitted from the nucleus of an unstable atom when that nucleus loses energy.
- After alpha or beta decay, a daughter nucleus may remain in an excited state.
- The nucleus can move to a lower-energy state by emitting a gamma photon.
- Gamma emission changes nuclear energy but does not change proton number or nucleon number.
- Nuclear energy gaps are usually much larger than atomic gaps, so nuclear transitions often produce high-frequency gamma radiation.
Energy determines frequency
- Photon energy and frequency are related by E=hfE=hfE=hf, where EEE is energy in joules, hhh is the Planck constant and fff is frequency in hertz.
- A larger energy change produces a higher-frequency photon.
- Changes in atoms and nuclei can therefore generate electromagnetic radiation across a wide frequency range.
Comparing two transitions
Transition A releases 3.0×10−19 J3.0\times10^{-19}\,\text{J}3.0×10−19J and transition B releases 6.0×10−14 J6.0\times10^{-14}\,\text{J}6.0×10−14J.
Since f=Ehf=\dfrac{E}{h}f=hE, transition B produces the higher-frequency photon.
Transition A is consistent with an atomic transition, while transition B is consistent with a nuclear transition.
Describe the change precisely
Identify whether an electron or an excited nucleus changes state.
State that moving to a lower energy state emits a photon.
Link a larger energy difference to a higher frequency using E=hfE=hfE=hf.
Do not state that gamma emission removes protons or neutrons; it removes excess nuclear energy without changing proton number or nucleon number.
- How can an atomic electron produce a photon?
- What determines photon energy?
- How is gamma radiation produced?
- What stays constant during gamma emission?
