Two students debate how emission and absorption spectra can be used to build an…
CHEMISTRY · Multi-part · CBSE · Chemistry · Structure of Atom · Structure of Atom
Problem
Two students debate how emission and absorption spectra can be used to build an energy-level diagram for an atom. Student A claims that the ground state should always be assigned an energy of 0eV, while Student B asserts that the energy of a completely free electron should define the zero of energy, making all bound states negative.
Consider an isolated atom whose spectroscopic data include both a measured ionization energy and several discrete photon wavelengths from bound–bound transitions.
(a) Explain how the choice of reference point (ground state versus free electron) changes the numerical values that appear on an energy-level diagram but does not alter any physically measurable transition energies.
(b) Describe a systematic procedure for determining the energies of at least three bound states using only the known photon wavelengths and the ionization energy. Your description should make clear how you would handle the reference-point issue raised by the students.
(c) Discuss one experimental situation in which reporting energy levels relative to the free-electron reference is more informative than using the ground-state reference, and one situation in which the opposite is true.