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Chapter 5 Electrons in Atoms

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Greek Idea Democritus and Leucippus Matter is made up of indivisible particles Dalton - one type of atom for each element

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Thomsons Model Discovered electrons Atoms were made of positive stuff Negative electron floating around Plum-Pudding model

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Rutherfords Model Discovered dense positive piece at the center of the atom Nucleus Electrons moved around Mostly empty space

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Bohrs Model Why dont the electrons fall into the nucleus? Move like planets around the sun. In circular orbits at different levels. Amounts of energy separate one level from another.

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Bohrs Model Nucleus Electron Orbit Energy Levels

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Bohrs Model Increasing energy Nucleus First Second Third Fourth Fifth } Further away from the nucleus means more energy. There is no in between energy Energy Levels

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Light The study of light led to the development of the quantum mechanical model. Light is a kind of electromagnetic radiation. Electromagnetic radiation includes many kinds of waves All move at 3.00 x 10 8 m/s ( c)

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Parts of a Wave Wavelength Amplitude Origin Crest Trough

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Parts of Wave Origin - the base line of the energy. Crest - highest point on a wave Trough - Low point on a wave Amplitude - distance from origin to crest Wavelength - distance from crest to crest Wavelength - is abbreviated Greek letter lambda.

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Frequency The number of waves that pass a given point per second. Units are cycles/sec or hertz (hz) Abbreviated the Greek letter nu c = c =

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Wavelength and Frequency

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Frequency and Wavelength Are inversely related As one goes up the other goes down. Different frequencies of light is different colors of light. There is a wide variety of frequencies The whole range is called a spectrum Movie Flame Test Movie Flame Test

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Radio waves Micro waves Infrared. Ultra- violet X- Rays Gamma Rays Low energy High energy Low Frequency High Frequency Long Wavelength Short Wavelength Visible Light

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Aurora Borealis Energy entering the earths atmosphere causes gas atom electrons to become excited. When they fall to the ground state they give of photons of light. MovieMovie Aurora Movie

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Atomic Spectrum How color tells us about atoms

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Prism White light is made up of all the colors of the visible spectrum. Passing it through a prism separates it.

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If the light is not white By heating a gas with electricity we can get it to give off colors. Passing this light through a prism does something different.

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Atomic Spectrum Each element gives off its own characteristic colors. Can be used to identify the atom. How we know what stars are made of. Movie Emission Spectrum Movie Emission Spectrum

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Atomic Emission Spectrum

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These are called discontinuous spectra Or line spectra unique to each element. These are emission spectra The light is emitted given off.

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Light is a Particle Energy is quantized. Light is energy Light must be quantized These smallest pieces of light are called photons. Energy and frequency are directly related.

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Energy and Frequency E = h E = h E is the energy of the photon is the frequency is the frequency h is Plancks constant h = x Joules sec. joule is the metric unit of Energy

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The Math in Chapter 5 Only 2 equations c = c = E = h E = h Plug and chug.

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Examples What is the wavelength of blue light with a frequency of 8.3 x hz? What is the frequency of red light with a wavelength of 4.2 x m? What is the energy of a photon of each of the above? Given h = x Joules sec and the Speed of light equals 3.00 x 10 8 m/s ( c)

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An Explanation of Atomic Spectra

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Where the Electron Starts When we write electron configurations we are writing the lowest energy. The energy level where an electron starts from is called its ground state. Movie Energy Levels Movie Energy Levels

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Changing the Energy Lets look at a hydrogen atom

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Changing the Energy Heat or electricity or light can move the electron up energy levels

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Changing the Energy As the electron falls back to ground state it gives the energy back as light

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May fall down in steps Each with a different energy Changing the Energy

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{ { {

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Further they fall, more energy, higher frequency. This is simplified The orbitals also have different energies inside energy levels. All the electrons can move around. Ultraviolet Visible Infrared

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What Makes These Glow?

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What is light Light is a particle - it comes in chunks. Light is a wave- we can measure its wave length and it behaves as a wave If we combine E=mc 2, c=, E = 1/2 mv 2 and E = h If we combine E=mc 2, c=, E = 1/2 mv 2 and E = h We can get De Broglies equation = h/mv The wavelength of a particle.

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Matter is a Wave Does not apply to large objects Things bigger than an atom A baseball has a wavelength of about 1x m when moving 30 m/s 1x m when moving 30 m/s An electron at the same speed has a wavelength of 1x cm Big enough to measure.

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The Physics of the Very Small Quantum mechanics explains how the very small behaves. Classic physics is what you get when you add up the effects of millions of packages. Quantum mechanics is based on probability because

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Heisenberg Uncertainty Principle It is impossible to know exactly the location and velocity of a particle. The better we know one, the less we know the other. The act of measuring changes the properties.

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Measuring an Electron To measure where an electron is, we use light But the light moves the electron And hitting the electron changes the frequency of the light

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Moving Electron Photon Before Electron Changes Velocity Photon Changes Wavelength After

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The Quantum Mechanical Model Remember energy is quantized and comes in chunks. A quanta is the amount of energy needed to move from one energy level to another. Since the energy of an atom is never in between there must be a quantum leap in energy. Schrodinger derived an equation that described the energy and position of the electrons in an atom.

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Atoms Are Never In Between Levels

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Things that are very small behave differently from things big enough to see. The quantum mechanical model is a mathematical solution It is not like anything you can see. The Quantum Mechanical Model

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Has 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. an electron a certain distance from the nucleus. The Quantum Mechanical Model

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The atom is found inside a blurry electron cloud An area where there is a chance of finding an electron. Can be divided into smaller regions in the electron cloud. The Quantum Mechanical Model

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Atomic Orbitals Principle Quantum Number (n) = the energy level of the electron Within each energy level the complex math of Schrodingers equation describes several geometric shapes. The group shape is called the sublevel s,p,d,f Individual shapes are the electron orbitals The orbitals represent regions where there is a high probability of finding an electron.

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Sublevels and Energy Levels

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1 s orbital is found on every energy level found on every energy level Spherical shaped Each s orbital can hold 2 electrons Called the 1s, 2s, 3s, etc.. orbitals. The 1,2 and 3 designate the energy levels. s Sublevel

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6s Sublevel

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Alkali metals all end in s 1 Alkaline earth metals all end in s 2 really should include He, but it fits better later. He has the properties of the noble gases. s2s2 s1s1 S- block

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s, p, d, & f blocks

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p Sublevel Start at the second energy level 3 different directions 3 different shapes Each can hold 2 electrons

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6p Sublevel

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s & p orbitals for neon Glencoe Chemistry Matter and Change 2002, page 137

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The P-block p1p1 p2p2 p3p3 p4p4 p5p5 p6p6

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Each row (or period) is the energy level for s and p orbitals

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d Sublevel Start at the third energy level 5 different shapes Each can hold 2 electrons

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6d Sublevel

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Transition Metals -d block d1d1 d2d2 d3d3 s1d5s1d5 d5d5 d6d6 d7d7 d8d8 s 1 d 10 d 10

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d orbitals fill up after previous energy level, so first d is 3d even though its in row d

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f Sublevel Start at the fourth energy level Have seven different shapes 2 electrons per shape

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f Sublevel

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6f Sublevel

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F - block inner transition elements

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f orbitals start filling at 4f f 5f

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s, p, d, & f blocks

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6g Sublevel Sublevel g starts on the 5 th level. 9 shapes 18 electrons max ac.uk/chemistry/ orbitron/

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Summary s p d f # of shapes Max electrons Starts at energy level SL

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By Energy Level First Energy Level only s orbital only 2 electrons 1s 2 Second Energy Level s and p orbitals are available 2 in s, 6 in p 2s 2 2p 6 8 total electrons

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By Energy Level Third energy level s, p, and d orbitals 2 in s, 6 in p, and 10 in d 3s 2 3p 6 3d total electrons Fourth energy level s,p,d, and f orbitals 2 in s, 6 in p, 10 in d, and 14 in f 4s 2 4p 6 4d 10 4f total electrons

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By Energy Level Any more than the fourth and not all the orbitals will fill up. You simply run out of electrons The orbitals do not fill up in a neat order. The energy levels overlap Lowest energy fill first.

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Writing Electron Configurations the Easy Way Yes there is a shorthand

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Electron Configurations repeat The shape of the periodic table is a representation of this repetition. When we get to the end of the column the outermost energy level is full. This is the basis for our shorthand.

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The Shorthand Method Write symbol of the noble gas before the element, in [ ]. Then, the rest of the electrons. Aluminums full configuration: 1s 2 2s 2 2p 6 3s 2 3p 1 1s 2 2s 2 2p 6 3s 2 3p 1 previous noble gas Ne is: 1s 2 2s 2 2p 6 so, Al is: [Ne] 3s 2 3p 1

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The Shorthand Again Sn- 50 electrons The noble gas before it is Kr [ Kr ] Takes care of 36 Next 5s 2 5s 2 Then 4d 10 4d 10 Finally 5p 2 5p 2

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Increasing energy 1s 2s 3s 4s 5s 6s 7s 2p 3p 4p 5p 6p 3d 4d 5d 7p 6d 4f 5f Aufbau Diagram shows the energy of each sublevel and the order they fill with electrons Each box represents an atomic orbital

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Electron Configurations 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 - different spins

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Electron Configuration Hunds Rule- When electrons occupy orbitals of equal energy they dont pair up until they have to Lets determine the electron configuration for Phosphorus Need to account for 15 electrons

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The first two electrons go into the 1s orbital Notice the opposite spins Same as Helium 1s 2 only 13 more Increasing energy 1s 2s 3s 4s 5s 6s 7s 2p 3p 4p 5p 6p 3d 4d 5d 7p 6d 4f 5f

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The next electrons go into the 2s orbital Be on periodic table Be on periodic table 1s 2 2s 2 only 11 more Increasing energy 1s 2s 3s 4s 5s 6s 7s 2p 3p 4p 5p 6p 3d 4d 5d 7p 6d 4f 5f

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The next electrons go into the 2p orbitals Neon on periodic table 1s 2 2s 2 2p 6 only 5 more Increasing energy 1s 2s 3s 4s 5s 6s 7s 2p 3p 4p 5p 6p 3d 4d 5d 7p 6d 4f 5f

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The next electrons go into the 3s orbital Mg on periodic table Only 3 more 1s 2 2s 2 2p 6 3s 2 Increasing energy 1s 2s 3s 4s 5s 6s 7s 2p 3p 4p 5p 6p 3d 4d 5d 7p 6d 4f 5f

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Increasing energy 1s 2s 3s 4s 5s 6s 7s 2p 3p 4p 5p 6p 3d 4d 5d 7p 6d 4f 5f The last three electrons go into the 3p orbitals. They each go into separate orbitals 3 unpaired electrons 1s 2 2s 2 2p 6 3s 2 3p 3

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The easy way to remember 1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 5f 6s 6p 6d 6f 7s 7p 7d 7f 1s 2 2 electrons

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Fill from the bottom up following the arrows 1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 5f 6s 6p 6d 6f 7s 7p 7d 7f 1s 2 2s 2 4 electrons

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Fill from the bottom up following the arrows 1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 5f 6s 6p 6d 6f 7s 7p 7d 7f 1s 2 2s 2 2p 6 3s 2 12 electrons

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Fill from the bottom up following the arrows 1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 5f 6s 6p 6d 6f 7s 7p 7d 7f 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 20 electrons

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Fill from the bottom up following the arrows 1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 5f 6s 6p 6d 6f 7s 7p 7d 7f 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 38 electrons

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Fill from the bottom up following the arrows 1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 5f 6s 6p 6d 6f 7s 7p 7d 7f 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 6s 2 56 electrons

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Fill from the bottom up following the arrows 1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 5f 6s 6p 6d 6f 7s 7p 7d 7f 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 6s 2 4f 14 5d 10 6p 6 7s 2 88 electrons

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Fill from the bottom up following the arrows 1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 5f 6s 6p 6d 6f 7s 7p 7d 7f 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 6s 2 4f 14 5d 10 6p 6 7s 2 5f 14 6d 10 7p electrons

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Exceptions to the Rule in Electron Configuration

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Orbitals Fill Order Lowest energy to higher energy Adding electrons can change the energy of the orbital Half filled orbitals have a lower energy Makes them more stable Sometimes changes the filling order

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Write These Electron Configurations Titanium - 22 electrons 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 2 Vanadium - 23 electrons 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 3 Chromium - 24 electrons 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 4 is expected But this is wrong!!

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Chromium is Actually 1s 2 2s 2 2p 6 3s 2 3p 6 4s 1 3d 5 Why? This gives us two half filled orbitals Slightly lower in energy Holds true for other group 6 elements Cr, Mo, W, and probably Sg The same principal applies to copper Cu and group 11 elements

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Transition Metals -d block d1d1 d2d2 d3d3 s1d5s1d5 d5d5 d6d6 d7d7 d8d8 s 1 d 10 d 10

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Cus Electron Configuration Copper has 29 electrons so we expect 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 9 But the actual configuration is 1s 2 2s 2 2p 6 3s 2 3p 6 4s 1 3d 10 This gives one filled orbital and one half filled orbital. Same is true for Silver Ag and Gold Au and probably Unununium Uuu

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Lewis/Electron Dot Diagram

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