2Light and Quantized Energy (5.1) The study of light led to the development of the quantum mechanical model.Light is a kind of electromagnetic radiation EM).All move at 3.00 x 108 m/s (c) Speed of light.
3Parts of a waveCrestWavelengthAmplitudeOriginTrough
4Parts of Wave Crest - high point on a wave Trough - Low point on a waveAmplitude - distance from origin to crestWavelength (l) - distance from crest to crest. To calculate use: l=c/v.c = speed of light (3.00 x 108 m/s).V = frequency (HZ)
5FrequencyFrequency (v) is the number of waves that pass a given point per second. Units are cycles/sec or hertz (Hz). To calculate use:v = c/l
6Frequency and wavelength Are inversely related (v = c/l )As one goes up the other goes down.Different frequencies of light show as different colors of light.The whole range is called the electromagnetic (EM) spectrum
7Spectrum Low energy High energy Radio waves Microwaves Infrared . Ultra-violetX-RaysGamma RaysLow FrequencyHigh FrequencyLong WavelengthShort WavelengthVisible Light
8Light is a ParticleLight is energy, Energy is quantized, therefore, Light must be quantized.These quantized pieces of light are called photons.Energy and frequency of the photons are directly related. E = h x n(i.e.. High frequency = high energy)
9Energy and frequencyA photon is a particle of EM radiation with no mass that carries a quantum of energy. To calculate its energy use:EPhoton = h x nE is the energy of the photonn is the frequencyh is Planck’s constant (6.626 x Joules sec).
10Photoelectric EffectIn the photoelectric effect , electrons, called photoelectrons, are emitted from a metals surface when light of a certain frequency shines on it. (solar calculator)Can be used to identify the type of metal.
11ExamplesWhat is the frequency of red light with a wavelength of 4.2 x 10-5 cm?What is the wavelength of KFI, which broadcasts at with a frequency of 640 kHz?What is the energy of a photon of each of the above?
12Atomic Emission Spectrum How color tells us about atoms?The atomic emission spectrum of an element is the set of frequencies of the EM waves emitted by atoms of the element.Each is unique to the individual element giving a pattern of visible colors when viewed through a prism.
13PrismWhite light is made up of all the colors of the visible spectrum.Passing it through a prism separates it into colors.
14If the light is not white By heating a gas or with electricity we can get it to give off colors.Passing this light through a prism shows a unique color pattern
15Atomic Emission Spectrum Each element gives off its own characteristic colors.Can be used to identify the atom.This is how we know what stars are made of.
16These are called line spectra unique to each element.These are emission spectraMirror images are absorption spectraLight with black missing
25UltravioletVisibleInfraredThe Further the electrons fall, the more the energy and the higher the frequency.
26Light is also a wave Light is a particle - it comes in chunks. Light is also a wave- we can measure its wave length and it behaves as a waveThe wavelength of a particle is calculated using l = h/mv . (de Broglie equation)
27DiffractionWhen light passes through, or reflects off, a series of thinly spaced lines, it creates a rainbow effect because the waves interfere with each other.
62Diffraction Light shows interference patterns What will an electron do when going through two slits?If it goes through one slit or the other, it will make two spots.If it goes through both slits, then it makes an interference pattern.
70} Bohr’s Model Further away from the nucleus means more energy. Fifth There is no “in between” energy levelsFifthFourthThirdIncreasing energySecondFirstNucleus
71The Quantum Mechanical Model Energy is quantized. It comes in chunks.Quanta - the amount of energy needed to move from one energy level to another.Quantum is the leap in energy.Schrödinger derived an equation that described the energy and position of the electrons in an atomTreated electrons as waves. De Broglie equation predicts wave characteristics of moving particles. (l = h/mv)
72The Quantum Mechanical Model Does have energy levels for electrons.Orbits are not circular.It can only tell us the probability of finding an electron a certain distance from the nucleus.
73The Quantum Mechanical Model The electron is found inside a blurry “electron cloud”An area where there is a chance of finding an electron.Draw a line at 90 % probability.
74Atomic OrbitalsPrincipal Quantum Number (n) = the energy level of the electron (1,2,3,4,5).Within each energy level, there are sublevels that have specific shapes (s, p, d, f)Sublevels have atomic orbitals. These are regions where there is a high probability of finding an electron. (s=1,p=3,d=5,f=7)Each orbital can hold up to 2 electrons. Electrons held: s=2, p=6, d=10, f=14
75“S” orbitalsAn atomic orbital is a three-dimensional region around the nucleus that describes the electrons probable location.There is one “s”orbital for every energylevel (1s,2s,3s,4s,5s).*It is Spherical shaped and can hold 2 electrons each.
76“P” orbitals Starts at the second energy level (2p,3p,4p,5p) Dumbbell shaped (3 types)Each can hold 2 electrons (6-total)
81Maximum Number of Electrons (orbital x 2) SummaryEnergy Level(n)Number of orbitals(Odd 1,3,5,7)Sublevels(S, p, d, f)Maximum Number of Electrons (orbital x 2)12s12SP132626103SPd135SPDf26101441357
82By Energy Level First Energy Level only s orbital only 2 electrons totalWritten as 1s2Second Energy Levels and p orbitals are available2 in s, 6 in pWritten as 2s22p68 total electrons total
83Filling order Lowest energy level fills first. Each box gets 1 electron before anyone gets 2.Orbitals can overlapCounting systemEach box is an orbital shapeHas Room for two electrons
84Increasing energy 7s 2p 3p 4p 5p 6p 7p 3d 4d 5d 6d 6s 5s 4f 5f 4s 3s
85Increasing energy 7p 6d 5f 7s 6p 5d 6s 4f 5p 4d 5s 4p 3d 4s 3p 3s 2p
86Electron Configurations (5.3) Shows the way electrons are arranged in atoms.Aufbau principle- electrons enter the lowest energy first.This causes difficulties because of the overlap of orbitals of different energies.Pauli Exclusion Principle- at most 2 electrons per orbital - opposite spins
87Electron Configuration Hund’s Rule- When electrons occupy orbitals of equal energy they don’t pair up until they have to .Let’s determine the electron configuration for PhosphorusNeed to account for 15 electrons
88Increasing energy 7p 6d 5f 7s 6p 5d 6s 4f 5p 4d 5s 4p 3d 4s 3p The first to electrons go into the 1s orbitalNotice the opposite spinsonly 13 more
89Increasing energy 7p 6d 5f 7s 6p 5d 6s 4f 5p 4d 5s 4p 3d 4s 3p The next electrons go into the 2s orbitalonly 11 more
90Increasing energy 7p 6d 5f 7s 6p 5d 6s 4f 5p 4d 5s 4p 3d 4s 3p The next electrons go into the 2p orbitalonly 5 more
91Increasing energy 7p 6d 5f 7s 6p 5d 6s 4f 5p 4d 5s 4p 3d 4s 3p The next electrons go into the 3s orbitalonly 3 more
92Increasing energy 7p 6d 5f 7s 6p 5d 6s 4f 5p 4d 5s 4p 3d 4s The last three electrons go into the 3p orbitals.They each go into separate shapes3 unpaired electrons1s22s22p63s23p3
102Exceptions to Electron Configuration (optional)
103Orbitals fill in order Lowest energy to higher energy. Adding electrons can change the energy of the orbital.Filled and half-filled orbitals have a lower energy.Makes them more stable.Changes the filling order of d orbitals
104Write these electron configurations Titanium - 22 electrons1s22s22p63s23p63d24s2Vanadium - 23 electrons 1s22s22p63s23p63d34s2Chromium - 24 electrons1s22s22p63s23p63d44s2 is expectedBut this is wrong!!
105Chromium is actually 1s22s22p63s23p63d54s1 Why? This gives us two half filled orbitals.
106Chromium is actually 1s22s22p63s23p63d54s1 Why? This gives us two half filled orbitals.
107Chromium is actually 1s22s22p63s23p63d54s1 Why? This gives us two half filled orbitals.Slightly lower in energy.The same principle applies to copper.
108Copper’s electron configuration Copper has 29 electrons so we expect1s22s22p63s23p63d94s2But the actual configuration is1s22s22p63s23p63d104s1This gives one filled orbital and one half filled orbital.Remember these exceptionsd4s2 d5 s1d9s2 d10s1
109In each energy levelThe number of electrons that can fit in each energy level is calculated withMax e- = 2n2 where n is the energy level1st2nd3rd