3 What is light? Light consists of electromagnetic waves. Electromagnetic radiation includes:
4 Electromagnetic Radiation Consist of particles that move as waves of energyElectromagnetic radiation (EM radiation or EMR) is a form of energy emitted and absorbed by charged particlesCharge particle has an electric field surrounding itAs the particle moves it creates a magnetic field
5 Waves can be described by amplitude, wavelength, and frequency Amplitude – height of the waveWavelength(l) – distance between crestsFrequency(n) – number of wave cycles to pass a given point in a certain amount of timeWaves moving and 3-d but we’ll model.
6 Draw a Wave in the Box Measure the wavelength and amplitude. Then draw waves in box B of the same amplitude but greater frequency.What happened to the wavelength from A to B.How are wavelength and frequency related? How is energy related to frequency?
7 Using the equation: c = ln Find the wavelength of a radio wave that is brodcasted at 95.5 x 106HzFind the frequency of blue light. Blue light has a wavelength of 6.43x 10-7m.
8 Which are not visible?Which are more energetic than visible light? How do you know?What do all the rays in the electromagnetic spectrum have in common?
9 Compare the atomic models of Thomson and Rutherford. Do Now:Compare the atomic models of Thomson and Rutherford.Explain the Bohr model of the atomWhat colors make up the continuous spectrum of visible light?p362
10 Neils Bohr Studied hydrogen and its emission spectrum Proposed the Planetary ModelElectrons orbit the nucleusElectrons travel in successively larger orbits and when an electron jumps from an outer orbit to an inner one, it emits light.
12 Each element emits a unique collection of lines. The atomic spectrum can be used to determine the composition of a material, since it is different for each element of the periodic table.
13 Why do we so only certain lines of color? Each color has a specific wavelengthEach wavelength is associated with a specific amount of energyThat energy is released when the electron jumps from a higher energy level to a lower energy level.Only specific energy levels are allowed in the atom! Energy of the atom is quantized!
14 Chapter 5, Figure 5.4 Electrons absorb a specific amount of energy to move to a higher energy level. When electrons lose energy, photons with specific energies are emitted.Energy of quantum of electromagnetic radiation is proportional to frequency
15 So the electron behaves like a wave, but where is it? Werner Heisenberg proposed Heisenberg uncertainty principleThere is a limitation to knowing where the electron is (its position) and where its going (its momentum)Erwin Schrodinger developed a mathematical equation to describe the electron’s wave-like behavior
16 Probability of finding electron at different points is calculated Some points will have higher probability than othersIf connect all points of high probability, three dimensional shapes are formedThe most probable place to find the electron will be some place in that shapeAtomic orbitals
17 Zip Code07080The fourth and fifth digits representing a group of delivery addresses within that regionFirst digit (0-9) represents a group of states in the US. 0 is northeastern states and 9 is western statesSecond and third numbers represent a region in that group, perhaps a large cityQuantum numbers are used to describe locations of high probability of finding the electrons
18 3. Last to an orbital. 6d __ __ __ __ __ Orbital Diagram 5f __ __ __ __ __ __ __7s __1. Assign electrons to an Energy Level6p __ __ __5d __ __ __ __ __4f __ __ __ __ __ __ __2. Next to a sublevel:spdf6s __3. Last to an orbital.5p __ __ __4d __ __ __ __ __5s __4p __ __ __3d __ __ __ __ __4s __3p __ __ __3s __2p __ __ __2s __1s __
19 Atomic OrbitalsRegion around nucleus where electrons are likely to be foundEach orbital holds two electronsThese electrons have opposite spin
21 Follow 3 rules to configure the electrons 1. Aufbau Principle - electrons fill orbitals starting at the lowest available (possible) energy states before filling higher states2. Pauli Exclusion Principle - two electrons cannot share the same set of quantum numbers within the same system. Therefore, there is room for only two electrons in each orbital and the electrons have opposite spin.3. Hund’s Rule – in equal energy orbitals, arrange the electrons to achieve the maximum number of unpaired electrons.