- Electromagnetic Radiation
- Form of energy that moves as waves.
- Encompasses all types of light.
- Wavelength
- Greek small letter lambda
- Crest to crest or trough to trough.
- Measured in nanometers but most formulas require meters.
- Frequency
- Number of reapeating waves that cross at a given point in time.
- Measured in 1/s or s^-1 or hertz (Hz)
$$velocity = lambda * frequency$$
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Lambda and velocity are inversely proportional.
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In a vacuum, velocity = c (speed of light) (3.00*10^8 m/s)
- Spectroscopy
- Interaction between light and matter
- EM radiation absorbed or emitted
- A good differentiating characteristic.
- The resulting graph is called a spectra or spectrum.
Reflected light is transmitted or emitted?
- Absorbed
- EM radiation a sample takes in
- Transmitted
- EM radiation that passes through the sample w/o being absorbed.
- Emitted
- EM radiation reflected off the sample.
- Radiation given off by the sample when hit with radiation.
Color Theory
- Color Theory
- Mixing opposite colors results in a neutral gray.
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- Opposites are colors across from each other in the color wheel.
- Absorbed
- The opposite color.
- Transmitted
- What we see.
Assumptions
- Energy is proportional to frequency
- E = h * frequency
- E is energy in J
- h is plank's const - 6.626 * 10^-34
- = frequency
- Energy Transfer Occurs in Whole Integer Amounts
- Photons are singular packets of energy.
- E = h * frequency describes the energy of one photon.
- Quantized
Light Matter Interactions
- Photons vs. electrons
- Energy Absorbption Diagram
- n = 1 = ground state
- n > 1 are excited states - higher orbitals.
Electrons gain energy when they absorb photons.
When electrons move back to lower energy levels - they emit light at wavelength of how much energy was released from the sytem.
- Chemical bonds are formed from electrons.
- Electron bonds break when they get excited - energy input.
- Different bonds give different spectra graphs.
- Spectra graphs are useful for identifying molecular compounds which are made up of covalent bonds.
Covalent Bonds
- Hold atoms w/ electrostatic interactions.
- Bond Length
- At equillibrium between attractive and repulsive forces.
- Bond Strength Bond Dissociation Energy
- Energy needed to separate bonds at that distance.
- Covalent Bonds
- Form between non-metal and non-metal - molecular compounds.
- Formed by sharing of electrons.
- Can be single, double, or triple bonded.
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- Represented by number of lines between two atoms.
- Every covalent bond is made up of two or more electrons, at least 1 from each atom.
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- Always in multiples of 2
- Atoms have a fixed bonding capacity depending on electrons
- Valency
- Bonding Capacity
- Dependent on location in periodic table.
- Orbitals
- Electrons are found in orbitals.
- Quantum Numbers
- Describe electrons and their orbitals
- n = principle quantum number
- l = angular-momentum quantum number
- m_l = magnetic quantum number
- m_s = spin quantum number
Each electron has a unique set of quantum numbers.