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Unformatted text preview: While you wait, please try the following problems: # electrons # neutrons # protons Shorthand Sn 118 Cu 2+ 64 O 17 H 1+ 1 Determines the identity element With #p, determines mass number With #p, determines the charge 50 68 50 35 29 8 9 27 10 1 50 29 8 1 2- Light exists as a wave Waves come in all different sizes and colors Long wavelength Short Wavelength Wavelength = Section 2.1 Frequency So we can measure a waves frequency ( ) , or how many waves pass a given point in one second frequency ( ) = # waves/sec All light waves travel at the same speed, the speed of light (c) Section 2.1 Shorter Wavelength HIGHER FREQUENCY ( more waves/sec) Section 2.1 Frequency Longer Wavelength LOWER FREQUENCY ( less waves/sec) Long Wavelength = Low Frequency Short Wavelength = High Frequency c = c is the speed of light (m/s) is wavelength (m) is frequency (s-1 or hertz) Section 2.1 Wavelength and Frequency speed = (wavelength)(frequency) constant! So, if you know wavelength, you know frequency and vice versa! The energy of the light depends on the frequency or wavelength of its wave E= h E= hc / E = Energy (J) h = Planks constant (J*s) = frequency (s-1 ) c = speed of light (m/s) = wavelength (m) Section 2.1 Wave Energy Energy = (constant)(frequency) = (constant)(speed)/(wavelength) Section 2.1 Wave Energy Long wavelength Low Frequency Low ENERGY Short wavelength High Frequency High ENERGY 10 6 Radio 10 10 10 14 10 20 micro infrared vis UV X-rays There is a continuum of light shown below, the electromagnetic spectrum. n=4 n=3 n=2 # nodes = n - 1 node node node node node node n=1 (2) (1) (0) (3) The more nodes, the higher the energy! Section 2.4 Waves and Nodes node node n=3 L = 1 / 2 n = 2L/n = 2 / 3 L L # nodes = n 1 = 2 Waves and Nodes Section 2.4 + What needs to happen when we add energy to a H atom? Nucleus---- Increasing r Increasing E When an H atom absorbs energy, its electron must move farther away from the nucleus. Recall Coulombs Law: E = q 1 q 2 r = (+1)(-1) = -1 Constant Increasing E causes absolute value of the right side to get smaller . So, r must get bigger. Section 2.2 Adding Energy to an Atom Is it that simple?...
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