3.5 Energy Levels and Spectra Flashcards
What is a rainbow
A natural display of the colours of the spectrum of sunlight
Raindrops split sunlight into a continuous spectrum of colours
What is the difference between using a tube of glowing gas as the light source instead of a filament lamp when looking at colour spectrums
We see a spectrum of discrete lines of different colours rather than a continuous spectrum
The wavelengths of the lines of a line spectrum of an element are characteristic of…
…the atoms of that element
How can we identify the element that produced the light from a line spectrum
By measuring the wavelengths
No other element produces the same pattern of light wavelengths
Why does every element produce a different pattern of light wavelengths
Because the energy levels of each type of atom are unique to that atom so photons emitted are characteristic of the atom.
What is each line in a line spectrum due to
Light of a certain colour and therefore a certain wavelength
The photons that produce each line all have the ______ energy, which is ______ from the energy of the photons that produce any other line.
Same
Different
Each photon is emitted when an atom de-excites due to…
… one of its electrons moving to an inner shell
If the electron moves from energy level E1 to a lower energy level E2, the energy of the emitted photon hf =
E1 - E2
What is the simplest type of atom
The hydrogen atom
One proton as its nucleus and one electron
General formula for the energy levels of the hydrogen atom relative to the ionisation level
E = - 13.6eV / n^2
Where n=1 for the ground state, n=2 for the next excited state etc.
When a hydrogen atom de-excites from energy level n1 to a lower energy level n2, the energy of the emitted photon is given by…
E = (1/n2^2 - 1/n1^2) * 13.6 eV
What does each energy level correspond to
The electron in a particular shell.
How was the energy level formula for hydrogen first deduced?
From the measurements of the wavelengths of the lines
Why are measurements of the wavelength of light important in branches of science such as astronomy and forensic science
They enable us to identify the chemical elements in the light source.
What was helium discovered from
The spectrum of sunlight
Pattern of lines in spectrum was observed at wavelengths that had never been observed from any known gas and were therefore due to presence of previously unknown element in the Sun.
How is helium produced
As a result of the nuclear fusion of hydrogen nuclei in the Sun
Named after Greek word ‘Helios’ for Sun
How is helium produced in the earth
As alpha particles from the radioactive decay of elements such as uranium.
Can be collected at oil wells and stored for use in fusion reactors, helium-neon lasers and for very low temperature devices.
What happens to helium in liquid state below a temperature of 2.17K
Becomes a superfluid
What is a superfluid
A fluid with no resistance to flow, which escapes from an open container by creeping - as a thin film - up and over the sides of the container
