CHE K121 Lecture Notes - Lecture 16: Rydberg Constant, Standing Wave, Photon

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24 Oct 2018

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Electronic structure of atoms: wave behavior, propagation of energy, peak to peak is called wave-length ( " , frequency ( " s 1. Of waves that pass a given point per second: the longer the wavelength the lower the frequency and vice versa. Electromagnetic radiation: all electromagnetic radiation traces at the same velocity: the speed of light ( c ) is " E = h : e - quantum energy; h = planks constant ; frequency ) At lower energy, electrons are not emitted: atomic emission, continuous vs. line spectra, for atoms and molecules, one does not observe a continuous spectrum (the. Rainbow , as one gets from a white light source. "1: only a line spectrum of discrete wavelengths is observed. Wednesday, october 24, 2018 unique line spectrum: hydrogen spectrum, johann balmer (1885) discovered a simple formula relating the four lines to integers, johannes rydberg advanced this formula a)

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LIGHT LAB SPRING 2018 CHEM 1430 Ill. Quantization of Electromagnetic Radiation In 1894, the German physidist, Max Plank, was working for a utility company to maximize visible light output from incandescent lamps using minimum power. Based on theoretical considerations, Planck postulated that electromagnetic energy could only be emitted at discrete values, rather than the continuum of predicted by classical physics, as multiples of the frequency of the radiation. Planck's Postulate took the mathematical form: EÂ·hv where the energy emitted, in Joules, is the product of a constant, h, known as Planck's Constant, and the frequency of the radiation, v. Planck's Postulate was experimentally verified and h found to have the value of 6.626 x 1034 Js(Joule seconds). The idea that electromagnetic radiation energy had specific frequency dependent energy was termed a "quantum of action," a distressing finding for the dlassically trained Planck. Despite his objections, Planck adopted this quantization of energy as a last resort to reconcile experiment with theory. This discovery set the stage for the early understanding of atomic structure, led to the term "photon" to describe the packet of energy carried by light waves, led to an understanding of the photoelectric effect, eventually leading to the development of general quantum theory Planck's Relationship, in combination with the tight equation, c the energy of a photon from frequency or wavelength. Î» w, allow expressions to be written to calculate ACTIVITY 4: QUANTIZATION OF THE ENERGY OF RADIATION To practice cakculations with Planck's Relationship, complete the following table, showing work with units in the right mest column, Convert given frequency to energy or given wavelength to energy. Take the value for Planck's Constant, h, to be 6.626 x 10"Js, show a calculation string include dimensions, reporting the final value to the proper number of significant figures Spectral Region Wavelength Frequency Energy in J/photon Show Calculation String Î» in meters v in s or cps X-ray 6.0 x 10"m Blue light 4.5 x 10m Infrared 4.1 x 10" cps Microwave 7.3 x 101 cps Radio Wave 3.0x 10 m IV. Bohr's Quantum Model for the Hydrogen Atom Ernest Rutherford's Gold Foil Experiment of 1911 demonstrated the nuclear structure of the atom. Questions remained as to how electrons were arranged in the atom. The most common belief called for the negatively charged the late 19h century recognized a particle (an electron) traveling around a body (the positively charged nucleus) would continuously radiate energy, slowing over time, eventually falling into the nucleus. Matter would collapse. Page 8 of 12

1) What is the objective of this experiment? (name of the experiment Atomic Absorption and Emission)

A) to create a calibration curve and solve for an unknown concentration of an element.

B) To illustrate the principles of emission and absorption.

C) All are correct.

D) to introduce Beer's Law.

2) Which of the following is NOT correct regarding electromagnetic radiation?

A) The energy of light is directly proportional to the frequency.

B) The speed of light is a constant number: 3 x 10^8 m/sec.

C) The speed of light equals the product of wavelength and frequency.

D) Longer wavelengths equal larger energies

3) Which of the following is NOT correct regarding the Bohr model of the atom?

A) Electrons in interior orbitals have a higher energy and those in the outter orbitals have lower energy.

B) It is a good model for the hydrogen atom but has shortcomings with more complex atoms.

C) When electrons absorb light, they are excited into the outter electron orbitals.

D) It is also called the 'planetary model'.

4) What is the molarity of a solution if 0.1044 moles of a chemical is dissolved in 789-mL of water?

5) Which of the following is NOT correct regarding Beer's Law?

A) Absorbance is directly proportional to concentration.

B) At high concentration, absorption and concentration do not have a linear relationship.

C) The molar absorptivity constant varies with the concentration of the solution.

D) As the concentration of a solution increases, the absorption of light increases.

CHE K121 Lecture Notes - Lecture 16: Rydberg Constant, Standing Wave, Photon

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