1st lecture - atomic structure Flashcards
what is chemical reactivity determined by
the movement of electrons between atoms
atoms cannot be
divisible
cannot be divided/separated
atoms consist of
charged particles
thompson made
plum pudding
electrons are the bits of plum
rutherford model
electrons orbit the nucleus
what was wrong with rutherfords model
- made it seem that all electrons are equal - challenged by atomic emission spectra
how does atomic emission spectra challenge rutherford
in AES: electrons absorb energy and become excited
they transition to higher energy levels within the atom.
if rutherford was right, this would not happen as there would be no higher energy levels due to all e- being the same.
what is the atomic emission spectra
spectra with different lines
light: wave or particle
excited e- transition to higher energy levels then return to their original levels by emitting energy in the form of photons (light)
equation for energy carried by a photon
energy =
Plancks constant x frequency
=
planks x speed of light / wavelength
planks constant
6.626 x 10^ -34
what does the atomic emission spectra show
shows lines that are unique to each element
what is E = hv tell us
eneegy = planks x frequency
photon energy isnt continuuous but quantised
its a multiple of “hv” meaning it has a discrete value
bohr atom
positive nucleus
e- in orbits at diff distances to the nucleus
e- cannot exist between orbits, they are quantised
what are orbits defined by
quantum number ‘n’
e- closer to the nucleus are
lower in energy
tightly bound
more stable
what is a transition
e- absorb energy
become excited
move to higher energy orbital
release energy in photons
relax back to original orbit
what does each line on the spectra correspond to
a transition
this is unique to each element
if an e- distance from the nucleus doubles (x2) the attraction
1/4s
greater distance = higher attraction
equation to find energy released when an H electron moves to diff orbits
E =
-2.178 x 10^-18
x (1/nf ^2) - (1/ni ^2)
how many orbitals are there in total
infinity
as u move further from the nucleus, (increasing n value) the energy levels..
get closer and closer and closer
n=1 series name
lyman series
UV light
1= bottom
lyman bc ur lying down at the bottom of the page
n=2 series name
balmer series
VISIBLE light
2 ashy knees that need balm
n=3 series name
paschen series
IR light
passion for Christ: father, son, Holy Spirit
general rule for guessing which transition involved the greatest release of energy
the one with the lowest final n value eg: 1 or 2
this is bc the orbits are spaced out the most here
which electron will emit a photon in the visible light spectrum
n=2
balmer series
what is still wrong with the bohr explanation?
- works with H only tbh
- doesnt explain periodic properties of the periodic table
- atomic spectra results are different using a magnetic/non magnetic field
electrons in magnetic field mass spectra
can make a transition to 3 slightly different energy levels
electrons in atomic spectra with no magnetic field
can only absorb 1 distinct wavelength of light
can only jump 1 distinct energy level
was planck studying waves or particles
waves
walk the Planck
was einstein studying waves or particles
particles
plancks equation for waves
energy = plancks constant x frequency
is frequency a property of waves or particles
waves
einsteins equation for energy
energy =
mass x speed of light^2
de broglie equation
planks/wavelength = momentum
wha does de broglie link
pure particle property and pure wave property.
combines planck and einsteins equations for particles and waves.
what is constructive interference
when 2 waves are in phase with each other
they reinforce eachother and their amplitude doubles
what is destructive interference
when 2 waves are out of phase and cancel each other out
what property do electrons and light share
wave particle duality.
- constructive + destructive interference which is a property of waves.
- photoelectric effect: light knocks electrons off a metal - particle property
summary of this set
e- have wave particle duality
meaning they have wave and particle properties
e- can move between orbits when energy is given these are called transitions and show up on atomic emissions spectra.
