3.4 - energy levels in atoms Flashcards
what is the energy of an e- in a shell like
constant
what is the energy of an e- closer to the nucleus like compared to the energy of an e0 further away
closer to the nucleus = less energy the e- has
what is the lowest energy state of an atom called
the ground state
how would you describe an e- that has moved up to a higher shell
its in an exited state
diagram of the energy levels of an atom
- label the possible axis
what do low-pressure gasses emit when they conduct electricity
light
describe de-excitation
an exited atoms e- in its excited state moved back down to its energy level where a vacancy was left
- emitting energy as a photon, so the atom becomes stable again
the equation to calc the energy of a photon emitted from an atoms e- de-exiting
hf = E1 - E2
- the difference in energy levels the e- drops
best way to calc the no of possible photon emission energies from an e- being excited from the ground state
start from the energy level the e- is excited to, draw arrows from here to the bottom then the next bottom …
continue then move along to the second highest and work downwards again
excitation by photon absorbs
- key points
if photons energy doesn’t - the diff between energy levels the atom will just immediately re-emit the photon
diagram and explain how fluorescents work
alternating current at electrodes boils e- off
- e- move back and forth the low-density mercury tube as they are attracted to the switching +ve cathode
if they gain enough Ek, they cause excitation by collisions with the mercury atoms
- the mercury atoms then de-excites emitting U. V. radiation. this then excites the phosphors coating by photons
- the prosperous de-excites in stages emitting photons of the visible sprecrum, overall white light is given off
why is low-density mercury used in fluorescent tubes
since if it was high density, the e- would collide too soon, no gaining enough Ek to cause excitation by collision,
they need the time to gain the needed energy
