2 Electromagnetic radiation – energy that travels through space as waves. Waves have three primary characteristics:Wavelength (- lambda) – distance between two consecutive peaks or troughs in a wave. Unit = meterFrequency ( = nu) – indicates how many waves pass a given point per second. Unit = Hertz (Hz)Speed – velocity (c = speed of light = 3 x 108 m/sec) - indicates how fast a given peak moves in a unit of timec =
3 Tell me what you know… Which wave has the greatest wavelength? Which wave has the greatest frequency?Which wave has the greatest speed?
4 Electromagnetic radiation (light) is divided into various classes according to wavelength.
5 Tell me what you know… Which color has the greatest wavelength? Which color has the shortest wavelength?
6 Wave- Particle Theory – Light as waves & Light as photons Photon/quantum – packet of energy OR a “particle” of electromagnetic radiation
7 Change in Energy of a photon = (Planck’s Constant) x (frequency) Energy - (E – change in energy) – Unit Joules (J)Planck’s Constant –(h = x J * s)Ephoton = hChange in Energy of a photon = (Planck’s Constant) x (frequency)c = & Ephoton = h →Ephoton = hcEx: What is the wavelength of light with a frequency of 6.5 x 1014 Hz? What is the change in Energy of the photon?E = hcΔE = 4.3 x JGiven= 6.5 x 1014 Hz = ? ΔE = ?= c= 3 x 108 m/sec6.5 x 1014 Hz= (6.626 x J x s)(3 x 108 m/s)4.6 x 10-7 mλ = 4.6 x 10-7 m
8 Tell me what you know…What does ΔE tell us about a photon?
9 Excited State – atom with excess energy Ground State – lowest possible energy stateWavelengths of light carry different amounts of energy per photonOnly certain types of photons are produced (see only certain colors)Quantized – only certain energy levels (and therefore colors) are allowed
10 Emission and Absorption Spectra Emission Spectrum – bright lines on a dark background. Produced as excited electrons return to a ground state – as in flame tests.Absorption Spectrum – dark lines in a continuous spectrum. Produced as electrons absorb energy to move into an excited state, only certain allowable transitions can be made. Energy absorbed corresponds to the increase in potential energy needed to move the electron into allowed higher energy levels. The frequencies absorbed by each substance are unique.NucleusNucleus
11 Tell me what you know…How can we tell elements apart using emission spectra?
12 Bohr Model – suggested that electrons move around the nucleus in circular orbits Only Correct for HydrogenWave Mechanical Model – Described by orbitals gives no information about when the electron occupies a certain point in space or how it moves *aka – Heisenberg's Uncertainty Principle
13 Parts of the Wave Mechanical Model 1. Principle Energy Level (n) – energy level designated by numbers 1-7.-called principle quantum numbers12345672. Sublevel – exist within each principle energy level-the energy within an energy level is slightly different-each electron in a given sublevel has the same energy-lowest sublevel = s, then p,then d, then fspdf
14 Tell me what you know…Write the sublevels in order of highest energy to lowest energy.
15 Parts of the Wave Mechanical Model cont. 3. Orbital – region within a sublevel or energy level where electrons can be founds sublevel – 1 orbitalp sublevel – 3 orbitalsd sublevel – 5 orbitalsf sublevel – 7 orbitals- ** No more than two electrons can occupy an orbital**-an orbital can be empty, half-filled, filled
16 Tell me what you know…How many total electrons are in each sublevel (s, p, d, & f)?
17 Sulfur = 1s2 2s2 2p6 3s2 3p4 Cd = 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 Electron Configuration – arrangement of the electrons among the various orbitals of the atom Ex: 1s22s22p6 = NeonSulfur =1s22s22p63s23p4Cd =1s22s22p63s23p64s23d104p65s24d10Na =1s22s22p63s1NeNa
18 Principle Energy Level SummaryPrinciple Energy Level# of sublevels# of orbitals presents p d fTotal # of orbitalsMaximum # of electrons1112224833918441632
19 Shapes of orbitals All s orbitals are spherical as the principle energy levelincreases the diameter increases.All p orbitals are dumbbell or figure-8 shaped – all have the same size and shape within an energy level
20 4 of the d orbitals are 4-leaf clover shaped and the last is a figure-8 with a donut – all have the same size and shape within an energy level
22 Electron Spin Spin – motion that resembles earth rotating on its axis– clockwise or counterclockwisePauli Exclusion Principle – two electrons in the same orbital must have opposite spinsHund’s Rule – All orbitals within a sublevel must contain at least one electron before any orbital can have twoOrbital Diagram – describes the placement of electrons in orbitalsuse arrows to represent electrons with spinline represents orbital (s=1, p=3, d=5, f=7)____ full ____ half-full ____ empty
24 Tell me what you know… Summarize each in four words or less: Spin Pauli Exclusion PrincipleHund’s Rule
25 Aufbau OrderAufbau Order – Tool to predict the order in which sublevels will fillOR use order on Periodic Table
26 Core Electrons – innermost electrons – not involved in bonding Noble Gas Configuration – Shorthand configuration that substitutes a noble gas for electronsEx:Valence Electrons – Electrons in the outermost (highest) principle energy level in an atom, electrons use in bondingCore Electrons – innermost electrons – not involved in bondingValence Configuration – shows just the valence electronsNa = 1s22s22p63s or [Ne]3s1Sn = 1s22s22p63s23p64s23d104p65s24d105p2 or [Kr]5s24d105p2Na = 3s1 3rd Shell/1valence electronSn = 5s25p2 5th Shell/4 valence electrons