CHEM 150 1nd Edition Chapter 6 : Electrons in Atoms and Periodic Properties Lecture 19Outline of Last Lecture • The gass Phase • The Kelvin scale (K)• Absolute Zero Outline of Current Lecture • To understand the quantum-mechanical model of an atom, we have to know about electromagnetic radiation.• Section 7.2: Light behaves as a wave. It has a frequency (v) and a wavelength (λ) that are related by its speed. It refracts and diffracts• It undergoes constructive and destructive interference. V.λ = Cc=2.99792458x10^8m/s• Section 7.4: But light also behaves like a particle. The photoelectron effect (pp 319-321), in particular, was best explained if light consisted of small “packets” of energy (photons).The energy of a photon is related to its frequency.E= v . h h= 6.62606931x10^-34J.sCurrent LectureQ: Rank the following in terms of increasing wavelength:- Gamma rays, microwaves, yellow lightA: Shortest LongestGamma rays < Yellow light < microwaves Q: Rank the following in terms of increasing energy of the photons:-green light, red light, X-raysA: Low energy High energyred light < green light < x-raysQ: Rank the following in terms of increasing frequency:-blue light, radio waves, ultraviolet lightA: Low energy High energy radio waves < blue light < ultraviolet lightQ: A metal exhibits the photoelectron effect when light with a wavelength of 325.0nm or less strikes it. What is the minimum energy required to remove an electron from this metal?A: E= c . h/λ2.9979246x10^8m/g x 6.62607x10^39J.g /325.0nm x 1x10^-9m = 6.112x 10^-19JQ: A Br-Br bond has a bond energy of 193kJ/mol. What is the longest wavelength of light that can break this bond? [Remember 1 mole = 6.022142x10^23A: 193KJ/1mol bonds x1000J/1KJ x 1mol/6.022142x10^22bonds =3.20484x10^-19Jλ= c . λ/E =2.9979246x 10^8 x 6.62607x 10^-34J.g/ 3.20484x10^-19=6.20 x10^-7m
View Full Document
Unlocking...