Physical Chemistry

What is the Rayliegh-Jeans Equation

dp (v,T) = pv(T) dv= (8pi kb T)/ c³ *v² dv

What was the problem with the Rayliegh-Jeans Equation

It worked well at low frequencies, but breaks down at higher frequencies. Called “UV breakdown”

What did Planck hypothesize?

The energies of the oscillators were discrete and had to be proportional to an integer multiple of the frequency; E=nhv where E is the energy, n is an integer, h is Planck's constant, and v is the frequency.

What was Planck’s equation for black body radiation

dp (v,t) = pv(T) dv = ((8 pi h) / c³ )* (v³/( e^hv/kbT) -1) ) dv

Using Planck’s blackbody equation, as h approaches 0

the equation becomes hv/kbT

Heinrich Hertz discovered the

photoelectric effect

The photoelectric effect is

UV light causes electrons to be emitted from the surface of a metal

In the photoelectric effect is there threshold frequency or threshold intensity?

frequency (v0)

What is the quantum mechanical result for the photoelectric effect

KE= ½ mv² = hv-phi and hv0= phi

What was Johann Balmer’s formula for wavenumber (“nu”) v. 1/n²

nu (wavenumber)= 8.2202×10^14 (1- 4/n²) Hz

Balmer’s equation can be written in terms of wavenumbers and cm^-1 by

nu tilde= 109680 (1/2² - 1/n²) cm^-1

What is the visible emission spectrum of atomic hydrogen called

Balmer series

Johannes Rydberg extended Balmer’s formula why?

to cover additional lines of the hydrogen spectrum outside of the visible region

What is Rdyberg’s formula

nu tilde= 1/wavelength = Rh (1/n² -1/n²) cm^-1

(smaller n goes first?)

Louis de Broglie proposed that light and matter obeyed what relation

wavelength= h/p = h/mv

The force of attraction of an electron according to Coulomb’s law is?

f= -e² / 4 pi permittivity of free space r²

centrifugal force = coloumb’s law

-e²/ 4* pi permittivity of free space r² = me v²/r

Bohr’s contribution was to make two assumptions:

1. He proposed the existence of stationary orbits that once in, the electron would not loose energy in a classical fashion

   1. The stationary orbits required an integer number of de Broglie wavelengths…they were circular standing waves

Bohr’s assumptions are expressed as

2pir= n*wavelength

2pir=n*wavelength can be written as

me*v*r=n*h/2*pi or me*v*r=n*h bar

h bar equals

h/2pi