Evidence for electronic configuration

Atomic emission spectra shows…

…quantum shell numbers

How to obtain emission spectra

• Use discharge tube

• Electric current passed through a sample of gas

• Electrical energy causes molecules to split into atoms

• Electrons given energy, get promoted to higher energy levels

• Electrons fall back down, emit light of characteristic frequencies

• Shown as lines of colour

• If there were no fixed quantum shells, there would be a continuous spectrum of colour

Successive ionisation energy graph and explanation

Jumps in ionisation energy between shells (not subshells) of the same atom due to electron being removed from a different shell

First ionisation energy graph and explanation

Jumps in first ionisation energy of successive elements across a period, shows presence of subshells (eg electron removed from a p subshell, not an s subshell)