Electromagnetic Radiation
- 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 repeating waves that cross at a given point in time.
- Measured in $$1/s$$ or $$s^{-1}$$ or hertz (Hz)
Equations
- Velocity of a Wave
- $$velocity = λ * ν$$
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Wavelength and velocity are inversely proportional.
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In a vacuum, velocity = c (speed of light) ($$3.00*10^8 m/s$$)
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- ν
- Frequency
- λ
- Wavelength in meters
- Energy is Proportional to Frequency
- $$E = h * ν$$
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- ν
- Frequency
- E
- Energy in J
- h Plank's constant
- $$6.626 * 10^-34$$
Assumptions
- Energy Transfer Occurs in Whole Integer Amounts
- Photons are singular packets of energy.
- E = h * frequency describes the energy of one photon.
- Quantized
Spectroscopy
- 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, not 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.
Light Matter Interactions
- Photons vs. electrons
- Energy Absorption 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.
Bonding
- Bonds
- Hold atoms w/ electrostatic interactions.
Covalent Bonds
- Covalent Bonds
- Form between non-metal and non-metal - molecular compounds.
- Formed by sharing of electrons.
- Can be single, double, or triple bonded, known as bond order.
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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 the number of valence electrons.
- Bond Length
- At equilibrium between attractive and repulsive forces.
- Bond Strength Bond Dissociation Energy
- Energy needed to separate bonds at that distance.
- 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.