Chapter 7(Exam 2) Flashcards
Isaac Newton
Was able to explain how and why rainbows appear. When sunlight passes through a prism, it is separated into its components. Colors recombined into white sunlight with a second prism
Fraunhofer lines
Dark lines that appear in the optical spectrum of the sun, shown to be absorption lines of atoms
Atomic emission spectrum
a series of bright lines produced by high temperature atoms
Atomic absorption spectrum
A series of dark lines produced when free, gaseous atoms are illuminated by a continuous source of radiation
Electromagnetic spectrum from smallest to largest wavelengths
gamma rays x rays ultraviolet rays visible waves infrared waves microwaves radiowaves
electromagnetic radiation
a form of energy that has wave characteristics and propogates through a vacuum at a characteristic speed(c)
amplitude
the height of the crest or depth of the trough of a wave
diffraction
bending of waves around obstacles
interference
the superposition of waves when they combine to form a new wave
refraction
the bending of waves as the change mediums
Max planck
explained blackbody radiation by assuming the energy emitted by heated solids is quantized
Photon
Quantum of electromagnetic radiation
Quantized/unquantized states
Quantized: discrete energy levels(steps)
Unquantized: Smooth transition between levels
Photoelectric effect
Phenomenon of light striking a metal surface and producing an electric current, explained by Albert Einstein using plancks equation
blackbody radiation
the amount of electromagnetic radiation emitted as a function of frequency as a result of heating solids
What happens if the radiation described in the photoelectric effect is below threshold energy?
no electrons are released
Threshold frequency
(vo) the frequency needed to dislodge electrons from the metal surface, unique to each metal
work function
the minimum energy required to produce the photoelectric effect
work function=h(vo)
What if the frequency exceeds the threshold frequency?
v>vo, kinetic energy of ejected electrons can be found by using KE=hv-work function
Wave-particle duality
Light/radiant energy has properties of both a wave and a particle
wave characteristics: has wavelength and frequencies
Particle characteristics: photoelectric effect, quantized packets of energy
Johann Balmer
Determined wavelengths of four brightest lines in the H emission spectrum
wavelength=364.5•(m^2)/(m^2-n^2)
n=2, m>n
Johannes Rydberg
Revised Balmer’s equation by changing wavelength to wavenumber
1/wavelength=(1.0097•10^-2 nm^-1)(1/n1^2 - 1/n2^2)
Wavenumber
1/wavelength, the number of cycles of the wave in a given length
Empirical formula for hydrogen atom spectrum and it’s alternate form
1/wavelength=R(1/na^2 - 1/nb^2)
R=Rydberg constant= 1.097373•10^7 nm^-1
nb>na, both are positive integers
v=C(1/na^2 - 1/nb^2)
C=Rc=3.29•10^15 s^-1
nb>na
Bohr’s number
En=-hcR(1/n^2)
hcR=2.179•10^-18
for one electron ions, use Z^2 instead of 1 with Z denoting the atomic number
Characteristics of electrons in H atoms
- Occupy discrete levels and exist only in the available energy levels
- Can move in between energy levels by absorbing or admitting energy
- Have energy levels designated by a specific value for n
Difference between energy levels formula
🔼E=-2.178•10^-18 J(1/nfinal^2 - 1/ninitial^2)
Ground/excited states for hydrogen atoms
Ground state: E1, lowest energy level
First excited state: E2
Second excited state: E3
etc.
Absorption/emission
Absorption: Transition from a lower to a higher energy state, +🔼E
Emission: Higher energy state to lower energy state, -🔼E
Bohr model strengths and limitations
Strengths
1. Accurately predicts energy needed to remove an electron from an atom(ionization)
- Allowed scientists to begin using quantum theory to explain matter at the atomic level
Limitations
1. Does not account for spectra of multielectron atoms
- Movement of electrons in atoms is less clearly defined than Bohr allowed
Wavelength/frequency formula
c=(wavelength)v
Difference between energy levels
🔼E=-2.178•10^-18(1/nfinal^2 - 1/ninitial^2)
