8) Atomic Energy Levels & Transitions Flashcards
Electrons with a range of kinetic energies strike atoms of a particular element which are in their ground state. As a result of these collisions photons of various frequencies are emitted by some of the atoms. Explain what is meant by the ground state of an atom and describe the process that is taking place in the atoms emitting photons.
- The ground state is the lowest energy state an electron can occupy.
- Electrons in atoms can only occupy discrete energy levels.
- Electrons collide with orbital electrons.
- Giving the electrons the energy necessary to move to a higher level.
- Electrons later return to a lower level/ground state losing energy.
- By emitting photons of discrete frequencies depending on the energy difference.
What is meant by an excited atom?
An electron that is at a higher level than the ground state.
Describe the process by which mercury atoms become excited in a fluorescent tube.
- Electrons flow through the tube.
- And collide with atomic electrons or mercury atoms.
- Raising the electrons to a higher level in the mercury atoms.
What is the purpose of the coating on the inside surface of the glass in a fluorescent tube?
- Photons emitted from mercury atoms are in the ultraviolet spectrum.
- These photons are absorbed by the powder.
- And the powder emits photons in the visible spectrum.
What must be done to validate the predictions of an unconfirmed scientific theory?
- A hypothesis needs to be tested by experiment.
- The experiment must be repeatable.
Explain the difference between excitation and ionisation.
- In either case, an electron receives exactly the right amount of energy.
- Excitation promotes an orbital electron to a higher energy level.
- Ionisation occurs when an electron receives enough energy to leave the atom.
An atom can also become excited by the absorption of photons. Explain why only photons of certain frequencies cause excitation in a particular atom.
-Electrons occupy discrete energy levels and need to absorb an exact amount of energy to move to a higher
level.
-Photons need to have a certain frequency to provide this energy.
-The energy required is the same for a particular atom.
-All energy of photon absorbed in 1 to 1 interaction.
When electrons in the ground state of hydrogen atoms are excited to the n = 3 energy level, photons of more than one frequency are subsequently released. Explain why different frequencies are possible.
Electrons return to lower levels by different routes not straight to ground state.
A fluorescent tube is filled with mercury vapour at low pressure. After mercury atoms have been excited they emit photons. In which part of the electromagnetic spectrum are these photons?
ultraviolet.
Why do the excited mercury atoms emit photons of characteristic frequencies?
-Mercury atoms have discrete energy levels.
when electrons change levels they lose a discrete amount of energy.
-Leading to photons of discrete frequencies.
State what is meant by ionisation energy.
The minimum energy to remove an electron from an atom from the ground state.
Explain why the energy levels are negative.
To remove an electron, energy has to be supplied.
Explain how the collisions of charged particles with gas atoms can cause the atoms to emit photons.
- Energy from the collision of charged particles transfers energy to electrons in gas molecules.
- Electrons excited to higher energy levels.
- The more energy the electrons absorb, the higher the energy levels reached.
Why do electrons de-excite and what do they do as they de-excite.
- Electrons are unstable at higher energy levels so will fall back down.
- When it falls it will emit a photon.
