EasyChemistryHigh School (11–12)Structure of the Atom › Light, Atomic Spectra and the Bohr ModelConceptualBoard ExamIB
One student heats hydrogen gas at low pressure and sees a few bright lines…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
One student heats hydrogen gas at low pressure and sees a few bright lines. Another heats a thin iron wire until it is white hot, and sees a smooth band of all colours. Why are the two spectra so different?
Need a reminder? The key ideaShow
Hydrogen's lines obey , with . Lyman ends on , Balmer on , Paschen on , Brackett on . From level , different lines are possible.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. The gas. Separate atoms can only jump between their own sharp energy levels, so only certain wavelengths appear: a line spectrum.
Step 2. The solid. Closely packed atoms disturb each other's levels into broad bands, and the hot solid gives out every wavelength: a continuous spectrum.
Answer: lone atoms give sharp lines from fixed levels; a hot solid gives a smooth band.
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