Practise using scattering and spectral evidence to infer atomic structure, identify nuclides and calculate photon properties from discrete energy-level transitions.
This question is in two parts. Part 1 is about the nuclear model of the atom and radioactive decay. Part 2 is about waves.
Part 1 Nuclear model of the atom and radioactive decay
Outline how the evidence supplied by the Geiger-Marsden experiment supports the nuclear model of the atom.
most undeflected/pass straight through;
hence mostly empty space;
few deflected;
hence small dense nucleus;
positive / positively charged;
This section consists of three questions: B1, B2 and B3.
Tritium may be produced by bombarding a nucleus of the isotope lithium-7 with a high-energy neutron. The reaction equation for this interaction is
Identify the proton number Z of X.
2;
This question is about atomic energy levels.
Describe the appearance of an atomic absorption spectrum.
continuous spectrum crossed by dark lines;
Explain why the spectrum in (a) provides evidence for quantization of energy in atoms.
dark lines formed by the absorption of photons;
the absorbed photons have specific/discreet wavelengths; indicating discreet differences in energy; which can only be explained by existence of energy levels;
The principal energy levels of the hydrogen atom in electronvolt ( eV ) are given by
where n is a positive integer.
Determine the wavelength of the absorption line that corresponds to an electron transition from the energy level given by n=1 to the level given by n=3.
E=13.6[121−321]=12.1eV;
12.1eV=12.1×1.6×10−19 J=λhc;
λ=102 nm or 103 nm ;
Marking guidance:
Award [3] for a bald correct answer.