CHEM 151 1st Edition Lecture 13 Outline of Last Lecture I. AtomsII. Atomic Number and Mass numberIII. IsotopesIV. Atomic MassOutline of Current Lecture V. Electrical InteractionsVI. Light InteractionsVII. Atomic Emission SpectraCurrent LectureProtons and electrons have the same charge, but are opposite in sign.Coulombs Law: F=q1q2/r2q= (+/-) 1.602 x 10-19 Coulomb (C) Electrons have potential and kinetic energy. Atoms are most stable when total energy is minimum.Electrons like to pair up, but only one pair per box.Because atoms have electrical nature, they can interact with light. What does light do?- Y-ray destroys tissue- X-ray penetrates tissue and knocks electrons out- UV moves electrons and breaks bonds- Visible moves electrons inside atoms (jumps)- IR causes molecules to vibrate; no electron jumping- Microwaves spin molecules and rotate bonds- Radio/TV passes through tissue- Long waves communicate through earthWhen the light emitted by individual atoms is passed through a prism, only a few colored lines are visible. (line emission spectrum)Excited atoms emit light of only certain wavelengths.Wavelengths of emitted light depend on type of atom.The wavelength can be used to calculate the energy difference between levels. Energy per photon:E=hv; h=6.6261 x 10-34 J*sλv=c; c=2.998 x 108
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