3.4- ENERGY LEVELS IN ATOMS Flashcards
What are the electrons of an atom trapped by?
electrostatic force of attraction of the nucleus
How do the electrons move about?
move about the nucleus in allowed shells/orbits, surrounding the nucleus
What is the energy of an electron in a shell closer to the nucleus like in comparison to an electron in a shell further away?
electron in a shell near nucleus has less energy than electron in shell further away from nucleus
What is an atoms ground state?
lowest energy state of an atom
What happens when an atom in the ground state absorbs energy?
one of its electrons moves to a shell at higher energy, so atom now in excited state
What can the excitation energy measurements be used to construct?
energy level diagram for the atom
What does an energy level diagram show?
the allowed energy values of the atom
What does each allowed energy of an energy level diagram correspond to?
certain electron configuration in the atom
If the ionisation level is considered as the zero reference level, what would the energy levels below it be like?
shown as negative values
What do gases at low pressure emit when they’re made to conduct electricity?
light
What does a neon tube emit when it conducts electricity?
red-orange light
What does the gas-filled tube used to measure excitation energies emit and when?
light when excitation occurs
Why is light emitted when excitation occurs in a gas-filled tube?
happens as the atoms absorb energy due to excitation by collision, but don’t retain the absorbed energy permanently
What is the electron configuration in an excited atom like?
unstable
Why is the electron configuration in an excited atom unstable?
an electron that moves to an outer shell leaves a vacancy in the shell it moves from
What happens to the vacancy in a shell when an electron moves from it?
vacancy filled by an electron from an outer shell transferring to it
What happens when the vacancy in a shell is filled by an electron from an outer shell transferring to it?
electron emits a photon
What is the process of de-excitation?
atom moves to a lower energy level
What is the energy of a photon emitted when an electron de-excites?
equal to energy lost by electron and so by atom
Can an atom de-excite indirectly?
yes
How can an atom de-excite indirectly?
via several energy levels if intermediate energy levels are present
How is the energy of an emitted electron calculated?
energy of emitted electron hf = E1 - E2
What can an electron in an atom do to move to an outer shell where vacancy exists?
absorb a photon
What must the photon be like for it to be absorbed by an electron in an atom to move to an outer shell where vacancy exists?
energy of photons is exactly equal to gain in electron’s energy
