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Chem 16 > Quantum Theory & Atomic Structure > Flashcards

Quantum Theory & Atomic Structure Flashcards

1
Q

electromagnetic radiation

what is wavelength & parts

3

A
  • length of wave
  • lambda
  • top=crest; bottom=trough
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2
Q

electromagnetic radiation

unit of wavelength distance

2

A

meters

pwede rin angstrom

1 A∘ = 1 x 10 -10m

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3
Q

electromagnetic radiation

what is frequency

A
  • how many crests/troughs that pass thru a given point per second (υ) in cycles/sec 1/time s-1 or Hz
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4
Q

electromagnetic radiation

what is speed (2)

meaning, speed

A
  • distance over time (m/s)
  • speed of electromagnetic radiation= 3 x10 8 m/s = speed of light (c)
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5
Q

electromagnetic radiation

equation for speed of electromagnetic radiation

A

c=υλ

speed=frequency*wavelength

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6
Q

electromagnetic radiation

what is amplitude

A

height of crest/trough from middle
related to intensity of radiation

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7
Q

electromagnetic radiation

what is the electromagnetic spectrum (2)

think of speed of waves electromagnetic spectrum & rainbow, their wavelength & frequency

A
  • all waves travel at the same speed thru vacuum but differ in frequency & wavelength
  • different wavelengths of visible light are seen as colors (increasing wavelength [4000-7000] but decreasing energy= blue to red)
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8
Q

3 phenomena that the wave model of light cannot explain

BPE & explain

A
  1. emission of light from hot objects or black-body radiation
  2. emission of electrons from metal surfaceson which light shines or photoelectric effect
  3. emission of light from electronically excited gas atoms to form emission spectra
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9
Q

describe hot objects and quantization of energy

A
  • heating of solids -> radiation (wavelength distribution of radiation depends on temperature)
  • relationship bet. temp, intensity, and wavelengths of the emitted radiation= solved by Max Planck (1900) thru “energy can be released or absorbed by atoms only in discreet ‘chunks’ of some minimum size (in quantums)”
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10
Q

what is a quantum

A

fixed smallest quantity of energy that can be emitted or absorbed as electromagnetic radiation

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11
Q

what is the equation of the energy of a single quantum

A

E=hυ

energy of a single quantum= planck’s constant x frequency

where energy is quantized hv, 2hv, 3hv, etc

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12
Q

what is the photoelectric effect

4 who, theory, what & assumption, limitation

A
  • by albert einstein (1905)
  • used planck’s quantum theory
  • EMR thru visible light to metal surface-> releases photoelectrons -> photoelectrons drawn to anode rod and current flows; assumed EMR is made of photons (from photons to photoelectrons)
  • there is a min frequency of light below w/c no electrons are emitted (because the individual photon interacting with an individual electron has insufficient energy to break it away)
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13
Q

what are photons (3)

meaning, proportion of energy to frequency, relation to quantum theory

A
  • light particles
  • energy of photon is inversely proportional to frequency of light
  • electromagnetic radiation is quantized
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14
Q

list of electromagnetic radiation

GaXU/LIM/RL

A

y rays, x rays, UV, visible light, IR, microwave, radiowaves (FM & AM), long radio waves

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15
Q

is light a wave or particles

A

macroscopically a wave but consists of collection of photons

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16
Q

what is the line spectra

2 who, what think rainbow

A

by bohr
when radiation is separated into differnt wavelength=spectrum (rainbow)

17
Q

what is the emission spectrum

A
  • formed by electric current passing thru a gas in a vacuum tube at very low pressure w/c causes gas to emit light (looks like DNA sequences)
  • aka bright line spectrum
  • each element has unique atomic spectrum=use to idetify elements (think hodgins)
  • johann balmer (1855) first to give formula to calculate the wavelengths in hydrogen spectra but extended to Rydberg equation [1/λ=RH(1/n1^2 - 1/n2^2)
    where λ=wavelength, RH=Rydberg constant (1.096776 x 10^7 m-1), n1 & n2 positive integers (n2>n1)
18
Q

what is the bohr model of the hydrogen atom

|6 what is bohr model, bohr + planck, think spdf, solar system & atom indian sounding vid, how electrons move in bohr model & planck eq, and atomic vs electromagnetic spectrum

A

electrons move in circular orbits around nucleus
adopted planck’s idea that energies are quantized (have values)
1. only orbits of certain radii, corresponding to certain definite energies are permitted for electrons in an atom (theres a limit of no. of electrons per orbit)
2. an electron in an allowed (stationary) energy state will not radiate energy and therefore will not spiral in nucleus
3. the electron can jump to another energy state by absorbing or emitting a photon (E=hυ)

atomic spectra is not continuous because the energy levels of electrons in atoms are quantized (has certain levels/line spectrum like when it completes 1 it auto goes to 2, not 1.001, or 1.5) compared to electromagnetic spectrum w/c is a continuous spectrum

19
Q

what is the equation for the calculation of energy based on bohr model (4)

remember double 18

A

E= (-2.18 x 10 -18J)(1/n^2)

where integer n=quantum numbers (radius increases as n increases)

lowest at n=1 (ground state

if electrons in higher energy state=atoms excited

20
Q

what is the equation for finding energy of photon

A

Ephoton=∆E atom=Efinal-Einitial=hυ

h=planks constant
υ=frequency

21
Q

what are the limitations of the bohr model

EW, EER, NA

A

correctly explains H emission spectrum but fails to address electron’s wave properties, electron-electron repulsion and nucleus attraction

22
Q

contribution of bohr model

2 think of bohr model and excited electrons

A
  • electrons exist in energy levels (described by quantum numbers)
  • energy=moving an electron from one level to another
23
Q

what is the wave nature of the electron

think duh brug lee; equation, conclusion

A

by louis de broglie (1925) thru de broglie relationship

λ=h/mv

λ= wavelength
h=planks constant
m=mass of particle
v= velocity of particle (momentum)

verified in 2 yrs by davisson & germer
all particles have particle & wave like character

24
Q

what is the quantum mechanical picture of the atom

small vs large objects in quantum mechanics

A

small particles follow quantum mechanics based on wave properties of matter

but cannot determine the paths that electron follows as they move about the atomic nuclei (thru uncertainty principle by werner heisenberg)

while larger objects follow laws of classical mechanics (newtons laws)

25
Q

what is the uncertainty principle

think double I: impossible & inverse

A
  • by werner heisenberg, german, in 1927
  • impossible to determine simultaneously both position and momentum of an electron or any small particle
  • the uncertainty in position of electron is greater than the size of the atom but if calcutated with ordinary mass, uncertainty is small & not significant
26
Q

what is the schrödinger’s equation and what for

A
  • h^2/8π^2m(δ^2Ψ/δ^2x + δ^2Ψ/δ^2y + δ^2Ψ/δ^2z) + VΨ=EΨ

h=plancks constant
m=mass
Ψ=wave function
V=potential energy
E=total energy
δ= small difference

calculates wave function/orbitals/states of electron

27
Q

how to interpret probability density of hydrogen

A

regions of high density of dots = high values of Ψ^2 = high probability of finding electrons

28
Q

what are the basic postulats of quantum mechanical theory

3, think spdf, plancks, & quantum numbers

A
  1. atoms and molecules can exist only in certain energy states thru quantisized energy (must emit/absorb enough energy to move to new energy state)
  2. energy change is related to frequency/wavelength of light - planck’s equation

E = hυ = hc/λ

  1. allowed energy states of atoms and molecules can be described by sets of number called quantum numbers - n,l,ml
29
Q

atomic spectra vs electromagnetic spectra

A

atomic spectra is line spectrum where its shows absorption & emission of electrons (where they fill energy levels) from electromagnetic spectrum

electromagnetic spectrum is a continuous spectrum of relative energies of the different frequencies or wavelengths

Chem 16 (3 decks)

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