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Atoms, Energy, Electrons, Oh My!! Chemistry February, 2011 Chapter 11 The Atom • What are the 3 parts that make up the atom? • Protons (+), neutrons, electrons(-) • Which particles make up the mass of the atom? • What does the atomic number on the periodic table tell us? • What is the electron’s job? • What can we say about a “group” of elements on the periodic table? Remembering Rutherford • Gold foil experiment that resulted in the “nuclear atom” • What about those electrons? Electromagnetic Radiation • To better understand the behavior of electrons, let’s look at the relationship between energy and light. • How does light travel? • In waves: energy is transmitted by light • Electromagnetic radiation. Electromagnetic Radiation • A wave has 3 important parts to it: • Wavelength :lambda, – The distance between 2 consecutive wave peaks • Frequency: nu, – How many waves per second • Speed of the wave through space – Speed of light = 2.99 x 108 m/s Electromagnetic Radiation • • • • • • Some examples of light waves: X rays Microwaves Radio waves They all differ in their wavelengths They all differ in the amount of energy transmitted Electromagnetic Radiation • Roy G. Biv Electromagnetic Radiation • What do you think has more energy, UV light or X rays? Electromagnetic Radiation • The length of the wavelength (and color) correspond to the amount of energy the wave carries. • The longer the wavelength of light, the lower the amount of energy • Compare the color of the cations of our flame test. • Na+ vs. Li+ • Which one has more energy as it is heated by a flame? Light: the Flip-flopper • Light: a bit of a “flip-flopper” • So light likes to travel through space in waves and transmit energy • Light also likes to behave like particles moving through space as photons, little packets of energy Flame test : revisited Hydrogen Hydrogen • • • • Let’s review some terms Atomic States: Excited state- atom with extra energy Ground state- atom in the lowest possible state • What happens to the H atom when it absorbs energy? • It enters an excited state! Hydrogen Hydrogen • What happens to the H atom when it releases the excess energy? Hydrogen • What is an Energy Level Diagram? • What does it show us? • The ground and excited states of a particular atom. • The energy of the photon emitted corresponds to the energy used by the atom to get to the excited state. Hydrogen • For each energy level the H atom travels, a specific photon is released • Why? Hydrogen • When specific photons are emitted, we see specific colors • Excited Hydrogen atoms always emit the same colors • What does this mean? • Hydrogen must have certain discrete energy levels. • This has a special name… Hydrogen • Quantized Energy Levels • Energy levels of all atoms are quantized: only certain energy level are allowed for each atom The Bohr Model of the Atom • Neils Bohr