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Atoms and Molecules > Exam 3 > Flashcards

Exam 3 Flashcards

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Organic Chemistry 101 flashcards
1
Q

Quantum Mechanics and why it was created

A

the study of anything small
* ex: subatomic, atomic, etc.
Quantum Mechanics was created because before, the equations at the time predicted that light that comes from a BBR that is glowing white would be infinitely intense and that anyone looking at a white light would be incinerated

Also, it was created to understand the structure of an atom

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2
Q

Electromagnetic Radiation

A

light energy
* Textbook definition: a form of energy transmission in which electric and magnetic fields are propagated as waves through empty space (a vacuum) or through a medium, such as glass

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3
Q

Energy (E)

A

property that must be transferred to do work

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4
Q

Kinetic Energy

A

energy in motion

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5
Q

Potential Energy

A

stored energy

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6
Q

Chemical Energy

A

energy stored in chemical bonds

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7
Q

Heat Energy (q)

A

energy due to a temperature change

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8
Q

Rainbow

A

full spectrum of white light (sunlight)

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9
Q

Speed of light (c)

A

Formulas:
* c = 𝜈 x λ
* c = 3.00 x 10^8 m/s
Unit:
* m/s

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10
Q

Blackbody Radiator

A

materials that glow when they get hot
* ex: coal, metals, sun
* produce continuous emission spectras

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11
Q

Photoelectric Effect

A
  • When light strikes the surface of certain metals, electrons are ejected
  • the energy of incoming light has to reach a certain threshold frequency before the electrons are ejected
  • the number of electrons emitted depends on the intensity of the incident light, but the kinetic energies of the emitted electrons depend on the frequency of the light
  • INTENSITY OF LIGHT DOES NOT AFFECT KE
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12
Q

Dual Nature of Light

A

describes light as a wave made out of particles
* light has particle-like properties (think of photons) and wave-like properties (think about the dispersion of light into a spectrum by a prism)

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13
Q

Photons

A

particles of light

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14
Q

Planck’s Model

A

Esingle photon = h x 𝜈
h= 6.63 x 10^-34 Jxs

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15
Q

Equation for kinetic energy flying off metal (photoelectron)

A

KE = h𝜈 - h𝜈initial
h𝜈 - energy given to the metal from the lamp
h𝜈initial - energy required to eject electron from the metal (threshold energy)

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16
Q

Waves

A

repetitive disturbances moving through a medium

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17
Q

Wavelength (λ)

A

distance from crest to crest or trough to trough
Equations:
λ = c / 𝜈
Unit: m or nm

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18
Q

Amplitude

A

height of the wave

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19
Q

Frequency (𝜈)

A

the number of waves that pass through a region per second
𝜈 = λ / c
Unit: Hz (1/s)

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20
Q

Wave interference

A

when two or more waves come in contact
* either constructive interference (creates a bigger wave) or destructive interference (creates a smaller wave)

21
Q

Constructive Interference

A

occurs when crests and troughs of a wave line up and they are in sync
* results in a new wave of larger amplitude
* think +

22
Q

Destructive Interference

A

occurs when waves are not aligned so the crest of one wave aligns with the trough of another
* results in either a new wave of smaller amplitude or the interacting waves cancel each other out
* think -

23
Q

Diffraction

A

patterns that result from wave interference

24
Q

In the diffraction pattern in water we observed in class…

A

bright spots meant constructive interference and darker spots represented destructive interference

25
Q

Standing wave

A

a wave that bounces back and forth within confinement
* ex: guitar string + think of the slinky experiment
Because standing waves are trapped/confined, they only exhibit a handful of wavelengths and frequencies. This relates to how we can only see certain waves through the spectroscope

26
Q

Emission

A

light given off by a material as a result of absorption of light/energy
*different than transmittance
*occurs when enough energy is absorbed by an atom, causing it to give off electrons, which then results in the emission of light

27
Q

De Broglie’s Wavelength (λd)

A

λd = h/p
p = momentum = mass x velocity
Unit = m or nm

27
Q

how we see colors

A

If you are blue, you are absorbing orange/red light (complementary color) and the blue light passes through

28
Q

Dual Nature of all Small Particles

A

De Broglie hypothesized that small particles of matter may at times display wave-like properties
(small = mass of an electron = 9.1 x 10^-31 kg)

29
Q

Dilution

A

adding solvent to increase the volume and lower the concentration of a sample
equation: c1 x v1 = c2 x v2

30
Q

Uncertainty of Wave Principle

A

when there are multiple waves…
* the location of the wave cannot be defined but the wavelength can be defined
when there is a single wave…
* the location of the wave can be defined but the wavelength can’t
THE MORE WE KNOW ABOUT LOCATION, THE LESS WE KNOW THE LENGTH OF THE WAVE
* Summarized by Heisenberg’s Uncertainty Principle
σx*σp ≥ h / 4π
* σx = uncertainty in location
* σp = uncertainty in momentum

31
Q

Bohr’s Model of the Atom

A

planetary model
* dense nucleus with neutrons and protons and electrons revolve around it like planets
* each orbit has a number (“n”) with the smallest orbit, closest to the nucleus n=1 n will always be a constant
* n 1 is the ground state and anything above it is an excited state.
* An atom emits energy as a photon when the electron falls from an orbit of higher energy and larger radius to an orbit of lower energy and smaller radius
* The radius of an orbit depends on the n #
rn = n^2 x a0
* a0 = Bohr’s radius 0. 53 x 10^−10m

32
Q

relationship of n and energy

A

electrons pass from one n-level to another using fixed amounts of E
low n-levels -> high n-levels = gain (absorb) energy
high n-levels -> low n-levels = lose (emit) energy
* En = -Rh/n^2
* △E = -Rh( 1/n^2f - 1/n^2i )
* * positive = absorbance and negative = emission

33
Q

Emission

A

Emission occurs when enough energy is absorbed by an atom, causing it to give off electrons, which then results in the emission of light.
* peaks pointing down on the substance’s atomic emission spectra graph
* you add energy to a substance like the elements in the discharge tube and they get excited and start to emit light.
* electron comes down n-levels

34
Q

Transmittance (T)

A

the amount of light that passes through a solution without being absorbed

35
Q

Absorbance (A)

A

the amount of energy/light taken in by particles in a solution
* has an inverse relationship with transmittance
* peaks pointing up on the substance’s atomic emission spectra graph
*the electron goes up an n-level

36
Q

Threshold frequency (Ф)

A

the minimum energy/frequency required by incoming light in order to eject or release electrons from the surface of a metal

37
Q

When an electron transitions to a higher n-level it (releases/gains)

A

Gains because they need more energy to go up in levels like you would need energy to climb up a ladder

38
Q

When an electron transitions to a lower n-level it (releases/gains) energy

A

releases, emission

39
Q

If something is glowing it is…

A
  • emitting light
  • an upwards peak on the substance’s emission spectra
40
Q

Interpreting Emission Spectra graphs

A

Where there are dips in the graph represent to where you

41
Q

λmax

A

the wavelength where the compound absorbs the maximum amount of light (photons)
* at this wavelength, a slight change in concentration allows for a significant change in the absorbance
* used for Beer’s law

42
Q

continuous vs discrete emission spectra

A

Black body radiators like the sun and coal have continuous emission spectrums (all of the colors/wavelengths present through spectrometer) while things like elements have discrete emission spectra (quantifiable).

This is because BBRs like sunlight and incandescent light have more different types of molecules/elements interacting w/ the light. Since the discharge tubes were concentrated with specific elements, the wavelengths that are transmitted are at specific points, representing the change in energy as electrons get as they change n-levels.

43
Q

How we see color

A

Things absorb wavelengths that correspond to their complementary color and transmit wavelengths (let pass through) of the color that they are
* ex: Red dye absorbs blue/green wavelengths and red wavelengths pass through

44
Q

Dye experiment vs discharge tube experiment

A

In Lab 5, the sharpness of the peaks was because the electrons of ATOMS are very specifically localized to energy levels, and their jumps between energy levels require specific energy changes

In lab 6 (food dyes), the peaks were broad because others are a lot of electrons in a MOLECULE and they’re all jumping around different MOLECULAR energy levels.

45
Q

Relationship between absorbance, concentration, and path length

A

When concentration increases, absorbance increases because there are more molecules present to interact with the light. As path length increases, absorbance increases because there are more molecules present and concentration also increases.
* ONLY FOR LOW CONCENTRATIONS AND ABSORBANCES BELOW 1
* at high concentrations, the molecules are no longer independent of one another

46
Q

gaps between energy levels

A

larger gaps between energy levels require shorter wavelengths of light (higher frequency and higher energy) for an electron to make that jump
-purple light - short wavelength, high frequency, high energy

47
Q

the energy of the electrons depends on the molecular structure

A

alternating single and double bonds make it so that electrons are shared across multiple bonds (delocalization)
*longer molecules have smaller energy gaps (changes in energy) between their energy levels and vice versa

Atoms and Molecules (7 decks)

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