Spectra, photons and wave-particle duality

Question 1

key facts about energy levels

Answer 1

• not the same as shells
• electrons can only exist in discrete energy levels
• lowest energy an electron can have in an atom = the ground state - n=1
• energy levels are labelled sequentially - n=1, n=2, n=3, …

Question 2

how are energy level diagrams labelled?

Answer 2

• labelled in eV or J
• these are negative - work needs to be done to move the electron up energy levels/totally remove it from the atom

Question 3

what is the significance of the ground state energy?

Answer 3

it is the lowest energy an electron can have in the atom
also equal to the ionisation energy - energy required to entirely remove the electron from the nucleus

Question 4

what is excitation?

Answer 4

when an electron gains the exact amount of energy required to move up one or more energy levels

Question 5

what is excitation by photon absorption?

Answer 5

when an orbital electron moves up an energy level(s) by abosrbing a photon with the exact same energy is the difference between energy levels
energy of photon absorbed: hf = ΔE

Question 6

what is excitation by collision?

Answer 6

• when an unbound electron collides with a bound/orbital electron , energy is transferred to the orbital electron
• if the kinetic energy of the colliding electron is greater than or equal to the difference between energy levels, the electron gets excited
• equation: ΔE < KE < E(ion)

Question 7

what is de-excitation?

Answer 7

when an electron moves down energy levels - it also emits a photon with energy equal to the difference in energy levels

Question 8

when does ionisation occur?

Answer 8

• when an electron gains enough energy leave the atom
• in an energy level diagram it is 0 energy - all other energy levels below it are negative - that the amount of energy needed to be gained for ionisation to happen