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Electromagnetic energy • Commonly known as light energy • Charged particles move in waves
The strength of the wave depends on its frequency and wavelength • Frequency: number of cycles that pass a point in a second • Wavelength: length of a single wave
the electromagnetic spectrum consists of light waves of different frequencies, ex. high-energy high-frequence X-rays (dangerous!) and low-energy low-frequency radio waves (harmless) • this includes a narrow strip of the visible spectrum: 700 nm ROYGBIV 400 nm, which we see as a rainbow
visible spectrum • the region of the electromagnetic spectrum that the human eye can detect, 400 nm to 700nm, made up of ROYGBIV
continuous spectrum • spectrum where all the wavelengths of light are present in an uninterrupted pattern of colours, ex. rainbow
line spectrum • a discontinuous spectrum, consists of distinct coloured lines rather than a rainbow • unique to an element
THE BOHR MODEL OF THE ATOM • Bohr developed his model of the atom to explain the line spectrum of hydrogen. • Bohr-Rutherford diagrams show the distribution of subatomic particles in an atom. They can be used to explain the behaviour of elements.
In the Bohr model, negative electrons orbit (circle) the positive nucleus as the planets orbit the Sun. An electron in each orbit has a specific energy.
electrons revolve around the atom's nucleus in orbits of fixed energy • electrons are restricted to certain energy levels • the energy of electrons is quantized: electrons must have a specific amount of energy at each energy level • an electron in its lowest energy level is in its ground state • an electron that absorbs enough energy to jump to a higher energy level is in its excited state
as the electron drops from the excited state to a lower energy level it loses energy in the form of electromagnetic radiation (light!!!!) • http://www.colorado.edu/physics/2000/applets/a2.html
Using the Bohr Model • for an atom to be stable it must have a) first energy level: 2 electrons b) second energy level: 8 electrons c) third energy level: 8 electrons