u3: quantum mechanical model of atom Flashcards
what did bohr’s model explain (postulates)
- periods result from filling of electron energy levels
- period comes to end when max numer of electrons are reached for outer level
- max number of electrons in each energy level are 2, 8, 18, etc
- group number provides number of valence electrons
why didn’t bohrs model work?
- explained one-electron systems, not more than 1 electron
- some elements have many spectra lines: bohr didn’t explain those liknes
what did albert michaelson find in 1891 abt bohr’s model
main lines of bright spectrum for hydrogen were acc composed of many lines
zeeman effect
if gas discharge tube placed near strong magnet, some single lines split into new lines
what did de broglie find?
- if light particles can behave like a wave, then all matter has internal wave-like properties
- radius of orbit = integer number of wavelengths = quantized energy level that bohr calculated
why wasn’t the wave-like nature of particles not observed
large particles have v small wavelengths
how does a beam of electrons behave when passing through a crystal? what was bohr’s problem?
- it diffracts the same way light diffracts when it passes through a glass prism
- bohr’s problem was treating electrons as particles
limit of wavelength
size limit of wavelength still in contention
schrodinger’s contribution
used eqn that explain particle and wavelike nature of electrons
what did schrodinger suggest about emission spectra?
that it results from electrons transforming from one orbital waveform to another, NOT electrons jumping from one energy level to another
which quantum numbers describe the possible energy states of an electron? wht r these states known as?
- n, l, ml, ms
- known as atomc orbitals that predict the 3D space (cloud) where there is a high probability of finding an electron in an atom
what did heisenburgs math lead to?
uncertainty principle
uncertainty principle
- position/speed of electron can’t be known w/ precision
- schrodinger’s orbital is acc a space/cloud where there is high probability to find electron
= quantum mechanical atomic model
what does the quantum mechanical model of the atom tell us?
- emission spectra for diff. elements (transofrming waves)
- why multivalent metal ions exist
- why some elements are magnetic
what doesn’t the quantum mech model include?
- atom has further subatomic particles
- subatomic particles mad of further subatomic particles (quarks)
- actinides don’t obey all of schrodinger’s rules when forming compounds
how are electrons arranged?
- by energy levels
- increasing from level 1 to level 7 period
what do electrons occupy?
orbitals, not orbits
what are orbitals
- energy cloud where electron spends 90% of its time
- not always circular in shape
principal
- n
- size
- 1 to infinity
- to describe atomic orbital
angular moment
- l
- shape
- 0 to n-1
- to describe atomic orbital
magnetic
- ml
- orientation/position
- -l to +l
- to describe atomic orbital
electron spin
- ms
- direction of electron spin
- +/- 1/2
- to describe electron in atomic orbital
pauli exclusion principle
no two electrons can have same value for n, l, ml, ms bc only two electrons of opposite spins can occupy the same orbital
how does n describe size of an atom?
- larger integer = larger size
- max. amnt of electrons tht energy level can occupy is 2n^2
how do values of l describe shape?
- 0 = s = sharp
- 1 = p = principal
- 2 = d = diffuse
- 3 = f = fundamental
subshell
collection of orbitals with same value of n and l
s orbitals
- spherical shaped
- each s orbital can hold 2 electrons
- s orbital for every enery level (called 1s, 2s, 3s, etc_
p orbitals
- dumb-bell shaped
- start in 2nd enery level
- p sublevel has 3p
- each orbital can old 2 electrons
d sublevel
- starts in 3rd energy level
- 5 diff shapes (orbitals)
- each orbital holds 2 electrons
f sublevel
- has 7 F orbitals
- starts in fourth energy level
- has seven diff. shapes (orbitals)
- 2 electrons per orbital
the 3 orientations for p orbital
- ml = -1 : along z-axis
- ml = 0 : along x-axis
- ml = 1 : along y-axis
how many orientations do s-orbitals have?
- 1
- bc. l=0 so ml=0
