Transcript opic 2.2
Electrons “in Orbit” Topic 2.2 The electromagnetic spectrum Know the following about the EM spectrum: • visible, infrared, and UV regions • describe the variation in: – wavelength – frequency – energy – colors for visible light Know what is in the red boxes The Electromagnetic Spectrum High frequency lower frequency Short wavelength longer wavelength High energy lower energy Continuous vs. Line Spectrum • continuous spectrum – produced by light as it passes through a prism • in the case of white light, all colors are seen • there are no levels • emission line spectrum – energy is applied to a specific element • this “excites” the element and the light is viewed through a spectroscope – a continuous spectrum is NOT observed, but a series of very bright lines of specific colors with black spaces inbetween instead – unique for every element and are used to identify atoms (much like fingerprints are used to identify people) More on emission line spectrum Give off energy when falls back down to normal energy level – the process • electrons surround the nucleus in specific orbitals or energy levels • when electrons are excited (heat/electricity) they can move to a higher energy level • when they move back down they emit energy in the form of electromagnetic radiation • because electrons can only exist in certain energy levels, only certain transitions can occur • the color of the light emitted depends on the frequency of the emitted photon • http://www.youtube.com/watch?v=QI50GBUJ48s this is a repetitive slide- just couldn’t bear to delete it 1. an electron in the atom gains (absorbs) energy from heating 2. electron jumps up an energy level. 3. electron is now unstable (unwelcome) in this level and is “kicked out” 4. when the electron loses the energy and come back to the original level, light is emitted The Atomic Emission Spectrum of Hydrogen • the emission spectrum of hydrogen is the simplest emission spectrum because there is only one electron – if had more than one electron, they would influence the other’s position – it is not uniform, but concentrated into bright lines, indicating the existence of only certain allowed electron energy levels – these four lines are called the Balmer series – McGraw Hill animation link convergence up here (levels are close together) More about energy levels • energy levels of atoms are NOT evenly spaced like the rungs of a ladder – the higher the energy level, the smaller the difference in energy between successive energy levels becomes – the energy difference between levels becomes less as the level number increases – this means that the lines of a spectrum will converge (get closer together with increasing energy) IB-- this is referred to as convergence of the spectral lines This is referred to as convergence of the spectral lines.