Unit 1 Flashcards
frequency
peaks per second in hertz (Hz) or s^-1… variable is v
speed of light
assuming a vacuum for this course… variable is c
wavelength
length from peak/trough of wave. can be nanometers or meters for units (use 10^9/10^-9 as conversion)
Electromagnetic Radiation Spectrum
shorter wavelength, higher frequency, higher energy
c= v(lambda)
inversely proportional c= speed of light constant v= frequency (waves per second) lambda= wavelength - don't forget to convert wavelength to match units of light
energy levels
are called shells, orbits or symbolized by “n”. lower orbitals have less energy ex (n= 1 has less energy than n=4)
distance between energy levels
- energy levels get closer together the further you go
electron goes down an orbital
- electron loses energy so it will emit light of wavelength equal to energy lost
electron goes up an orbital
electron absorbs energy equal to wavelength of light given to it
absorption
electron goes up shell due to energy given to it
emission
electron goes down shell due to energy emitted
continuous spectrum of light (line spectrum)
shows rainbow
- all wavelengths on spectrum are visible light
emission lines (line spectrum)
few colours on a black backdrop visually
- the colours are wavelengths of light emitted when a gas atom was originally excited but that then electron emits the light was it goes back to rest state
absorption (line spectrum)
while light is going through a gas sample of an element, the electron would absorb some energy of that light causing
at what speed does all electromagnetic radiation move at?
the speed of light
electromagnetic radiation and energy transfer
ex. when molecules absorb radiation, it increases the energy of the molecules causing more collisions and a rise in temperature (case of microwave at least)
planck’s quantum theory
energy can only be gained or lost in whole number multiples of hv where h is a constant. can find energy absorbed or released
quantum
small packet of energy that can only occur in discrete units. system can only transfer energy in whole quanta thus energy seems to have particulate properties.
photosns
einstein discovered that electromagnetic radiation can be seen as a stream of particles called photons
delta e=nhv OR delta e=hc/(lambda)
gives the amount of a single quantum (the energy of a photon of light)
n= an integer h= planck's constant v= frequency
dual nature of light
electromagnetic radiation can show certain characteristics of particulate matter which is called dual nature
de Broglie’s equation
lambda= h/mv
lambda= h/mv
used to calculate the wavelength for a particle
- h=planck’s constant
m= mass
v= AHAH it is velocity
1 joule equals
1 kg times m^2 / s^2
hydrogen emission line spectrum
shows that only certain energies are allowed for the electron in the hydrogen atom AKA the energy of the electron in hydrogen is quantized. changes in energy between discrete energy levels in hydrogen will produce only certain wavelengths of emitted light. if any energy level was allowed, the emission spectrum would be continuous
emission spectrum
emission: when hydrogen molecules absorb energy and some of the bonds are broken. this results in excitation of electrons which means they contain excess energy which they release by emitting light of various wavelengths to produce the emission spectrum
contains black but with some colour bars in between
if energy levels in atoms were not quantized
all light would be white (contains all wavelengths)
delta e= -2.178 times 10^-18 J times z^2 (1/n^2f-1/n^2i)
n= integer. larger n is larger orbit radius z= atomic number (usually 1 for hydrogen) f= final i= initial
this is negative when there is emission
e= -2.178 times 10^-18 J times (z^2/n^2)
gives the energy of each energy level
n=6 to n=1
n=1 has more negative energy because the electron in that level is more tightly bound to the smallest allowed orbit. the change in energy then is negative as energy is lost and electron is now in a more stable state. the energy is carried away from the atom by the production (emission) of a photon
bohr model
- model fits the quantized energy levels of the hydrogen atom and postulates only certain allowed orbits for the electron
- as electron becomes more tightly bound, its energy becomes more negative relative to the zero-energy reference state.
quantum model vs bohr
Bohr
Shells have set radii and electrons orbit the nucleus on those shell surfaces
Each energy level is a single shell
The shells surround the nucleus like planets surround the sun
Based on one number, the energy level, n
Quantum model
Each energy level is a collection of different orbitals/subshells (whose shape is defined by where you are most likely to find the electron 90% of the time)
Each orbital can hold 2 electrons
The orbitals have different complex shapes and electrons can travel anywhere within the space contained by the orbital
Each electron in an atom can be uniquely identified by 4 quantum numbers
quantum numbers
N
L
Ml
Ms
First three describe the orbital, the location of the electron
Last one describes the particular electron (spin number)
First Quantum Number, the principal quantum number
it is n (energy level)
n=1,2,3… (natural numbers, starting at 1)
N is the main factor in determining energy, it is not the only factor
Average distance from the nucleus (electron can literally be anywhere in orbital but mostly, on average, it stays at the n distance)
Higher n is more energy
Second Quantum Number, the secondary quantum number
it is l (orbital shape)
L (lowercase, cursive)= 0,…, (n-1) (whole numbers)
The “l” value represents a specific orbital shape/sub shell/ sub level
L = 0 → s orbital → sphere
L = 1 → p orbital → figure 8 or dumbell
L = 2 → d orbital → clover shape
L = 3 → f orbital → look up picture…
Possible values of L depends on which energy level you are looking at
Secondary factor of energy
Shape of orbital
Higher l is more energy
Which sub-levels (orbital shape) exists for the principal quantum numbers, 1-4?
Other levels do exist but there are the only orbital shapes that exist in ground state
Third Quantum Number, the magnetic quantum number
it is ml (orbital orientation)
Ml (lowercase m with lowercase l as subscript)= -l,…, l (integers)
Related to the orientation of the orbital in space relative to the other orbitals in the atom
Number of orbitals for that sublevel= number of orientation
___Letter equals orbital but don’t forget to say + and -!
