Chapter 3 Flashcards
order of electromagnetic spectrum
microwave -> infared -> visible -> ultraviolet -> x-ray -> gamma ray
highest to lowest wavelength
Microwaves –> Infrared –> Visible –> Ultra Violet –> X-ray –> Gamma Ray
highest to lowest frequency (same as highest to lowest energy)
gamma rays -> x-rays-> ultraviolet -> visible light -> infrared-> microwaves-> radio waves
Electromagnetic radiation
light has oscillating (repeating variations) electric and magnetic fields.
Light behaves as a…
wave
Wavelength
is the distance from one crest (point) to the next, (nm)
Frequency
Number of wavelengths that pass a point in a given period of time (s⁻¹ or Hz)
wavelength of visible spectrum
(order: ROYDBV)
red- 750 nm
Violet - 400 nm
As wavelength increases
Frequency decreases
As frequency increases
Wavelength decreases
What is Interference?
adding the amplitudes at each point in each point in space/time
Constructive Interference
The amplitude doubles and becomes twice as large
Equation for finding Wavelength and frequency using constant
c = λν(frequency)
Deconstructive Interference
the waves cancel out and it becomes flat
Equation for energy and wavelength
E = h(c/λ)
Equation for energy and frequency
E = hν
what is diffraction?
when waves pass through a slit, causing them to bend
showed that light is a wave as particles do not diffract
Single Slit Diffraction Experiment
light bended in waves when passing through a slit.
What can atoms do after absorbing energy?
Release it as light
Are the wavelengths that are emitted by light the same or different compared to the wavelengths absorbed by light?
SAME
Double-Slit Diffraction experiment
showed a larger wave-like pattern. proved light is a wave. The light interfered with itself to result in the bending (diffraction) pattern.
What is the photoelectric effect?
When you shine light on a metal surface, electrons are sometimes ejected
Rydberg equation explanation
to find wavelengths of the line spectrum of HYDROGEN or to find energy levels and transitions of an atom
Rydberg equation
1/λ = Rh/c (1/ni² - 1/nf²)
observations of photoelectric effect
- higher intensity(amplitude) light= more electrons ejected but same kinetic energy (KE is independent of intensity)
- electrons can only be ejected once the light is above a threshold frequency
-> higher energy (frequency) light = same number of electrons ejected but higher KE (linear relationship w KE and frequency)
Rh value positive vs negative
+ during absorption
- during emission
Bohr model
shows electrons orbiting the nucleus at different energy levels (n)
How can an electron move from one energy level to another?
Photon must be give exact amount of energy to promote electron from one orbital to the next
Einstein’s explanation 1905
- light energy behaves like particles known as photons
-work function is the energy it takes to escape the binding energy -> E of photon needs to be greater than the work function to accelerate off the atom
Light emission
Moving from higher energy level to lower energy level (closer to nucleus) (ex. n=5 to n=2)
Light Absorption
Moving from lower energy level to higher energy level (further away from nucleus) (ex. n=2 to n=4)
principal quantum numbers
symbol: ‘n’
represents the energy of the ‘shell’
integers ≥ 1
(ex. 2s, n=2)
Finding the energy of an electron equation
Energy of electron =
Efinal - Initial = hv = hc / λphoton
angular momentum number (of wave function)
symbol: ‘l’
shape of orbital ‘sublevel’
0→n-1 (integers)
(ex. 2s, l=0 (s) )
magnetic (of number)
symbol: Mι
orientation of orbital in space
-l→+l (integers, includes 0)
(ex. 2p: Mι= -1,0,+1
Finding the energy of absorption/emission equation
Energy of absorption/emission =
hc/λphoton = +/- Rh Z² (1/nfinal² - 1/ninitial²)
Spin of a orbital
symbol: Ms
‘spin’ of electron (it’s angular momentum), aligned along which axis, etc
±1/2
How accurate was Bohr’s model?
Bohr correctly related energy levels to quantum numbers in his model (explaining absorption and emission of energy) but FAILED to model the position and radii of electron orbits or the energies of multi electron systems
Pauli Exclusion Principle
“no electrons in an atom may have the same exact set of 4 QN’s simultaneously”
Wave-Particle Duality of Light
- Light behaves like a wave
-> exhibits interference and diffraction
-> has speed, wavelength, and frequency
-> intensity is measured w amplitude
-Light behaves like a particle
-> photoelectric effect
-> energy of photon is proportional to its frequency
- wave and particle nature of light are complementary properties
Finding the energy of the orbit equation
Eorbit = -2.18 x 10⁻¹⁸J (1/n²)
’s’ orbitals
l=0
Ml=0
spin=±1/2
typically spherical
has three axis, x, y, and z
de Broglie
proposed that electrons are both particles and waves
lambda = h/mv
- velocity must be in m/s
- mass should be in kg
‘p’ orbitals
l=1
Ml= -1,0,+1
spin=±1/2
three different planes: (i.e) 3px, 3py, 3pz
‘d’ orbitals
l=2
Ml= -2,-1,0,+1,+2
spin=±1/2
five different planes: (i.e.) 4dxy, 4dxz, 4dyz, 4d(x^2-y^2), 4d(z^2)
Heisenburg’s Uncertainty Principle
- measuring position precisely interferes with velocity and vice versa
- the product of the uncertainties must be at least h/4pi
‘f’ orbitals
l=3
Ml= -3,-2,-1,0,+1,+2,+3
spin=±1/2
seven different planes: (not required to draw)
Total nodes in an electron
n-1
Radial Nodes
n-l-1 (l being the angular momentum number)
Schrodinger’s cat
- until you observe a system, all possibilities coexist
- also known as observers effect
How do the differences in energy levels change as you increase energy level?
From n=1 to n=2 is biggest change in energy, from n=2 to n=3 much smaller change in energy, n=3 to n=4 is even smaller change in energy, etc.
Angular nodes
whatever l is
(ex. 2s: l=0, so there are 0 angular nodes in the orbital)
Schrodinger vs Bohr
- both try to describe the location and state of an atom’s electron
- both describe the electrons in orbit (schrodinger says they are waves in orbit though)
- both predict the same energy levels for hydrogen