Energy Levels

What are energy levels?

Electron shells

Describe the process of excitation

An electron absorbs energy from an incident photon and becomes excited, so moves up to a higher energy level.

What is required for excitation of an electron?

A photon with discrete (exact) amount of energy

Describe deexcitation

The electron moves down an energy level and emits a photon with energy equal to the difference in energy levels

What is meant by ‘ground state’?

The lowest energy level an electron can occupy

Why can only photons of certain frequencies cause excitation?

Energy levels are exact. Photons with the exact amounts of energy as an energy level will cause excitation, since E α f

What is meant by ionisation?

An electron is removed from an atom

Describe how an absorption spectra is made

A photon with a discrete amount of energy is absorbed by an electron to excite it to a higher energy level. The energy of the photon is inversely proportional to the wavelength (E = hc/λ)/ so the discrete wavelengths are less intense on the absorption spectrum as they have been absorbed.

Describe how an emission spectrum is made

An excited electron emits a photon with a discrete energy (hf = E_{1 -}E₂) as it deexcites and moves to a lower energy level. The energy of the photon is determined by its wavelength (E = hc/λ), so each wavelength relates to an emitted photon of discrete energy.

What provides evidence for discrete atomic energy levels?

Line spectra