Paper 3 Atomic Structure Answers

Q1 Spectral Line Counting

1. Number of downward transitions among 4 levels is $4(4-1)/2=6$. [2]
2. Some upper levels may be weakly populated, some transitions may occur much less frequently, and weak lines may fall below the detector’s sensitivity. Any two relevant points. [2]
3. $\lambda =1240/4.00=310\mathrm{nm}$. [2]

Q2 Specific Charge

1. $q/m=1.60\times 10^{-19}/6.64\times 10^{-27}=2.41\times 10^7\mathrm{C}\mathrm{k}{\mathrm{g}}^{-1}$. [2]
2. It compares charge effect relative to inertia, relevant for deflection by electric/magnetic fields. [2]
3. Charge doubles, so specific charge doubles if mass change is negligible. [1]