What happens to an atomic electron when an atom is excited?
It gains energy and moves to a higher permitted energy level without leaving the atom.
AQA A-level Physics (7408) · 3.2.2.2
Revise AQA A-level Physics (7408) specification point 3.2.2.2, Collisions of electrons with atoms, with free active-recall flashcards. Flip through the set or review every question and answer below.
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What happens to an atomic electron when an atom is excited?
It gains energy and moves to a higher permitted energy level without leaving the atom.
What condition must an incident electron meet to excite an atom in a collision?
It must have sufficient kinetic energy to supply the required energy.
What energy must be transferred to an atom to excite it between two permitted levels?
The energy transferred must match the difference between the two levels.
What happens when an excited atom returns to a lower energy level?
It can emit a photon whose energy equals the difference between the levels.
How does atomic ionisation differ from excitation?
Ionisation removes an electron, leaving it unbound and the atom as a positive ion. Excitation does not leave the electron unbound.
Under what condition can an incident electron ionise an atom in a collision?
It must transfer at least the energy required to remove an atomic electron.
What does the ionisation energy of an atomic electron depend on?
The atom and the electron’s initial state.
What gas does a fluorescent tube contain?
Low-pressure gas including mercury vapour.
What do accelerated electrons cause when they collide with atoms in a fluorescent tube?
Excitation and ionisation of the atoms.
How does ionisation help the gas in a fluorescent tube conduct current?
It produces free electrons and positive ions that help conduct the current.
What do excited mercury atoms emit as they return to lower energy levels?
Ultraviolet photons.
How does the fluorescent coating inside a tube produce visible light?
It absorbs ultraviolet radiation and emits visible light.
What is an electron volt (eV)?
The energy gained by an electron moving through a potential difference of one volt.
Approximately how many joules are in one electron volt?
How do you convert energy between electron volts and joules?