Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Laboratory 03Shedding Light on the Structure of the Atom1Objectives• Build and calibrate a simple spectroscope.• Use the spectroscope to observe the line spectrum of sodium; calculate the energy and frequency associated with the major transition(s).• Use the spectroscope to observe the line spectra of unknown substances and use line spectrum to identify substance.2Atoms are too small to be observed directly.Scientists in the late nineteenth and early twentieth centuries had to use indirect methods to decipher the architecture of individual atoms.3•Cathode ray tubes•Millikan’s oil drop experiment•Rutherford’s gold foil experimentAtomic model4A nucleus containing protons and neutrons, with electrons forming a relatively large “cloud” around the nucleus5Scientists have used the absorption and emission of light by matter, to determine the electronic structure of atoms.The electrons in the lower orbit move to the next level after absorbing a quantized amount of energy.Once the excited state electrons loose energy they emit light (various color depending on energy level) by releasing energy and coming back to its ground state.6Spectrum of the hydrogen atomWhen hydrogen gas (or other element) receive high energy spark it emits light with specific L-wavelength ,H2 (g) absorb energy (H-H bond breaks) - H atoms7Spectrum of the hydrogen atom8How are these lines generated?According to the Niels Bohr model, Electrons in an atom are locatedin fixed orbits that encircle thenucleus. An electron in a given orbit has a specific energy,m = mass of the electrone = charge of the electron ( -1.6022 x10-19 C)h = Planck’s constant (6.63 x 10-34 Js),b = 2.178 X10-18 J (combination of all constants in the equation). The variable n can have values 1, 2, . . . and is known as the principal quantum number. Each orbit has a different value of n .9According to the Bohr’s model the electron can only have an energy associated with one of the orbits; that is, the electron can never have an intermediate energy.Energy of an electron is quantized.The deference between the energies of the two orbits between which the electron moves reflects the amount of energy absorbed by the electron.10Hydrogen