U2 - Module 1: Analyzing Light-Matter Interactions Flashcards
What are the two types of light graphs?
- Absorption
- Emission
What is another term for light?
Electromagnetic (EM) Radiation
What is the process of light being absorbed?
- Light is shined on an object
- An object absorbs some of the light
- The light that reaches the other side of the object is dimmer.
What is the process of light being emitted?
- An object/element is heated up
- Light is emitted off of the object
Electromagnetic (EM) Radiation
Energy traveling through space as waves formed by oscillating electric and magnetic fields.
Wavelength
The distance between each wave
Frequency
How often a wave occurs
- # of waves per __
What is the symbol for wavelength?
λ (lambda)
What is the symbol for frequency?
v
What is the relationship between wavelength and frequency?
Inverse
- As wavelength increases, frequency decreases
(vice versa)
What is the formula for speed of light?
wavelength x frequency
What is the range of visible light?
400-700 nm
Ultraviolet light
Light that is lower than 400 nm
Infrared Light
Light that is greater than 700 nm
Why do atoms and molecules interact with EM Radiation?
They are made up of charged particles (electrons and protons)
What happens to energy when atoms/molecules interact with light?
Energy is absorbed or released
Spectroscopy
The analytical techniques based on the analysis of EM radiation absorbed/emitted by a chemical substance
Absorption Spectroscopy
EM Radiation is passed through an object and we measure the radiation that is absorbed
What does it mean when a wavelength region is not absorbed?
It is reflected
What happens to the color of an object when it absorbs all colors except 1?
The color of the object is the color of light that it reflected
What happens to the color of an object when it absorbs only 1 color but reflects the rest?
The color of the object is the opposite of the color absorbed on the color wheel.
What type of electromagnetic radiation has the shortest rays?
Gamma radiation
Does it take more or less energy to ionize an atom in the n=3 state, compared to ground state?
Less energy
- Atom is farther from the nucleus
- There are less attractive forces the further from the nucleus
What electromagnetic radiation has the longest wavelength?
Radio waves
What electromagnetic radiation has the shortest wavelength
Ultraviolet photon
What are the two graphs that represent absorbance of light?
- Absorbance
- Transmittance
What is the relationship between transmittance and absorbance?
The greater the level of transmittance, the lower amount of light being absorbed.
How does the transmittance graph work?
-The peaks of the graph go downwards
- The greater the dip, the larger amount of transmittance occurring
What does the light emission graph display?
The specific colors of light that are emitted when the material is heated up.
What does the number of wavelengths of light emitted mean?
The complexity of the molecule
- More wavelengths means a more complex molecule
What is unique about each atom?
Has its own set of emission spectra
What do the different colors of light emitted represent?
The different specific wavelengths the atom emits.
Quantization
Electrons exist in specific energy states
Explain the steps of quantization.
- The energy levels are quantized; electrons can only exist in the specific energy level, not between
- When a photon of light is absorbed that has an energy level of an exact difference between two energy levels, the electron jumps to a higher energy state.
- The electron remains in the higher energy state until it becomes unstable, and will eventually return to a lower state.
- As the electron moves back down to a lower energy level, it emits a photon with an energy equal to the distance of the energy level.
Emission
As the electron loses energy, it emits a photon of light that is equal to the amount of energy lost.
What level of photon light absorbed causes an electron to move to a higher energy state?
A photon with an energy level equal to the distance of the energy levels.
What causes electrons to move to higher energy levels?
Certain wavelengths absorbed (colors)
What color is not included in the quantization of wavelengths?
Yellow light
Why is a photon emitted after electrons move down energy levels?
There is excess energy in the atom due to moving down energy levels, and the excess is emitted through the photon.
What is the formula for finding energy transferred?
E = h (planck’s constant) x v (frequency)
What is the relationship between frequency and energy levels?
Directly proportional
- As energy increases, so does frequency
What is the relationship between wavelength and energy levels?
Inversely proportional
- As the wavelength increases, the energy decreases.
What unit is energy in?
Joules (J)
What value does “C” stand for?
The speed of light.
What value does “h” stand for?
Planck’s constant
How many kilojoules in 1 Joule?
1000 kJ
What do transitions with larger energy differences result in?
Shorter wavelengths
(higher energy photons)
Where can isolated atoms exist?
Different electronic energy states
What are the isolated atoms location dependent on?
How their electrons are distributed among different energy levels.
What changes the electrons energy state that they are in?
The absorption/emission of energy
What are the 3 different molecule excitation states?
- Electronic state
- Vibrational energy state
- Rotational energy state
Electronic Energy
Energy is associated with electrons in a molecule
Rank the order of energy required based off the 3 molecular energies changes.
- Electronic (highest)
- Vibrational
- Rotational (lowest)
What causes the transition in the electronic energy state?
Absorption/emission of photons
What light region is electronic energy found in?
- UV
- Visible
Rotational energy state
Energy is based off of the rotation of a molecule around its center of mass
What causes the transition in the rotational energy state?
Absorption/emission of low energy photons
What light region is rotational energy found in?
Microwaves
Vibrational energy state
Associated with the vibrations of atoms within a molecule (bonds stretch, break and twist)
What causes the transition in the vibrational energy state?
The absorption of IR radiation causes an increase in vibrational levels
What light region is vibrational energy found in?
Infrared
How do you convert from J of energy to kJ of energy?
Multiply the J of energy by avogadros #
Then divide by 1000
How do you convert from energy of a single photon to energy of a mole of photons?
Multiply the energy value by avogadros number
What must happen for a wavelength to move to a higher energy level?
Needs to give the SPECIFIC amount of energy to go from one level to another.
What is a mole considered?
A counting term
What happens when an electron loses energy?
The energy lost goes to making a photon of light equal to the same amount of energy lost.
Ground state
No excited electrons
