3.4 Energy Levels In Atoms Flashcards
Does an electron shell near the center of the nucleus have more or less energy than an electron further away from the nucleus
Has less energy
What is the ground state of an atom
The lowest state of energy of an atom
What is the excited stage
When an atom at ground state absorbs energy and one of its electrons moves to a shell at a higher energy
What does each energy allowed (excitation energy) correspond to
A certain electron configuration in an atom
What might the ionisation level be considered as
The zero reference level for energy instead of the ground state level
Energy levels below ionisation level would need to be shared as negative values
What happens to gas at a low pressure that are made to conduct electricity
They emit light
What colour is neon a metal when it conducts electricity
Red/orange light
What can A gas filled tube be used to measure
Excitation energy
Why is light emitted during deexcitation
Because the atoms absorb energy as a result of excitation by collision but they do not retain the absorbs energy permanently
Why is the electron configuration excited atom unstable
Because an electron moves to an outer shell leaves a vacancy in the shell that it moves from
What is the process of deexcitation
The vacancy is filled by an electron from the outer shell
when this happens the electron emitts a photon
the atom therefore moves to a lower energy level
What is the energy of a photon released by de excitation equal to
The energy lost by the electron and therefore by the atom
What is the energy of the emitted photon equal to
Hf = E1-E2
What must the photon have in order for an electron in the atom to move to an outer shell where a vacancy exists
The energy of a photon must be exactly equal to the gain of electrons energy
In other words the photon energy must be exactly equal to the difference between the final and the initial energy of the atom

What happens if the photons energy is smaller or larger than the difference between the two energy levels
It will not be absorbed by the electron
What can an atom in an excited state deexcite directly or indirectly to ground state regardless of
How the excitation took place
An atom can absorb photons of certain energies and then emitt photons of
Same or less energy
why do certain substances fluoresce or glow with visible light when they absorb UV radiation
Atoms in the substance absorb ultraviolet photons and become excited
when the atoms de-excite they emit visible light photons
what would happen if you removed UV radiation from a florescent object
It would stop glowing
what is a fluorescent tube
A glass tube with fluorescent coating on its inner surface
the tube contains mercury at a Low pressure
why does a fluorescent tube emit visable light (steps)
- ionisation and excitation of the mercury atoms occurs as they collide with each other and the electrons in the tube
- the mercury atoms emit ultraviolet photons as well as visible photons and photons of much less energy
- the ultraviolet photons are absorbed by the atoms of the fluorescent coating causing there excitation
- the coating atoms de excite in steps and emit visible light photons
why is a fluorescent tube much more officiant than filament lamp
a typical 100W filament lamp releases about 10-15W of light energy
the rest of the energy is lost to heat
fluorescent tube can produce the same light output with no kore than a few watts of power wasted as heat
what does a fluorescent tube have at each end
a filament electrode
why is a stater unit necessary in a fluorescent tube
because the mains voltage is too small to ionise the vapour in the tubes when the electrodes are cold
what happens when the tube is first switched on
the gas (argon) in the starter switch unit conducts and heats a bimetallic strip making it bend so the switch closes
the current through the starter unit increases enough to heat the filament electrodes
what happens when the bimetallic strip closes
the gas in the starter unit stops conducting and so the bimetallic strip cools and the switch opens
the mains voltage now acts between the 2 electrodes which are now hot enough for the ionisation of the gas to occur
what is wasted in a filament bulb and a low energy bulb when it emits about 15W of light
emits 75W
efficient wastes 5W
