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Unit 5 : Atomic Structure Dalton’s Atomic Theory(1803) 1) Elements are made up of tiny invisible particles called atoms. 2) Atoms of the same element are identical. Atoms of different elements are different. 3) Compounds are formed when atoms combine. Each compound has a specific number and kinds of atom. 4) Chemical reactions are rearrangement of atoms. Atoms are not created, destroyed, nor broken apart. Experiments to determine what an atom was • J. J. Thomson- used Cathode ray tubes • Clip of Cathode Ray Tube Thomson’s Experiment Voltage source - + Thomson’s Experiment Voltage source - + Thomson’s Experiment Voltage source n + Passing an electric current makes a beam appear to move from the negative to the positive end. Thomson’s Experiment Voltage source • By adding an electric field Voltage source + n By adding an electric field, he concluded that the particles were A. B. C. D. Positively charged Negatively charged Not charged Some negative and some positively charged Thomsom’s Model • Found the electron. • Couldn’t find positive (for a while). • Said the atom was like plum pudding (p. 101) (or Jello with fruit) • A bunch of positive stuff, with the electrons able to be removed. Spread out + charge Rutherford’s Experiment • Used _________to produce alpha particles. • Aimed alpha particles at gold foil by drilling hole in _______ container. • Since the mass is evenly distributed in gold atoms alpha particles should go straight through. • Used gold foil because it could be made atoms thin. Rutherford’s Experiment • After watching video, label the parts of his setup on your handout. Lead block Polonium Florescent Screen Gold Foil Alpha Particle What he expected Because Because, he thought the positive charge (and mass)was evenly distributed in the atom. (according to Thomson’s Model) What he got How he explained it • Atom is mostly empty • Small dense, positive piece at center. Rutherford just concluded that atoms have: A. Electrons B. Protons C. Neutrons D. a Nucleus + How he explained it • Atom is mostly empty • Small dense, positive piece at center. • Alpha particles are deflected by it if they get close enough. + + Modern View • The atom is mostly empty space. • Two regions • Nucleus- protons and neutrons. • Electron cloudregion where you might find an electron. Sub-Division of an Atom • Atom has two parts: Electron Cloud - space where electrons travel Nucleus - small, dense Center of atom Size of Atoms • Very small, drawing a line across a penny would cross over _______________ atoms • Diameter of 1 atom = 1x10-8 cm --or-A. 350,000 1 Angstrom (Å) B. 4 million C. 63 million -- or – D. 810 million 10 nanometers Size of Atoms • Most of atom is electron cloud • Nucleus is a very tiny portion of atom • Ratio, If an atom were the size of a football stadium, the nucleus would be the size of a pea ! Sub-Atomic Particles • • • • • ELECTRONS: Negatively charged Rotate around nucleus All electrons are identical Mass: insignificant compared to nucleus-0 Sub-Atomic Particles • • • • • • • Protons: Positively charged - same magnitude as eLocated in nucleus Mass: “heavy” compared to an electron All protons are identical If proton were 1 kg, electron would be 1 cg Mass = 1 atomic mass unit (amu) Sub-Atomic Particles • • • • • • Neutrons: Neutral - no charge Located in nucleus All neutrons are identical Mass: same as proton ( 1 amu) . Proton Neutron Electron 1 amu 1 amu 0 amu What the Numbers on Periodic Table Tell us about the Atom Atomic Number The number of Protons Equal to the number of electrons if atom is neutral Protons determine identity of Element Number of Protons does not change 1 H 1.0079 What the Numbers on Periodic Table Tell us about the Atom 1 Atomic Mass H 1.0079 Mass Number: • The Mass of an Atom (NOT found on Pd Table) • Mass of an atom = mass of the nucleus • Determined by counting Protons & Neutrons • Mass Number = # of Protons Ex: Oxygen + # of Neutrons Ex: Beryllium # of protons = 8 + # of neutrons = 8 # of protons = 4 + # of neutrons = 5 Mass Number = 16 Mass Number = 9 Your Turn: Mass Number Ex: Potassium # of protons = 19 + # of neutrons = Mass Number = 40 Enter the # of neutrons into your clicker Your Turn: Mass Number Ex: Potassium # of protons = 19 + # of neutrons = 21 Mass Number = 40 More Examples 2O Ex: Oxide ( ) Ex: Oxygen # of protons = # of electrons = # of neutrons = 8 8 8 Mass Number = 16 # of protons = # of electrons = # of neutrons = 8 10 8 Mass Number = 16 How many neutrons and electrons ? Your Turn: Number of Electrons Ex: Bromide (Br-) # of protons = 35 # of electrons = # of neutrons = Complete the Chart Mass Number = 79 How many protons, then enter the # of neutrons into your clicker? Your Turn: Number of Electrons Ex: Bromide (Br-) # of protons = 35 # of electrons = # of neutrons = 44 Mass Number = 79 Enter the # of electrons. Your Turn: Number of Electrons Ex: Bromide (Br-) # of protons = 35 # of electrons = 36 # of neutrons = 44 Mass Number = 79 Your Turn: Number of Electrons Ex: Magnesium (Mg+2) # of protons = 12 # of electrons = # of neutrons = 13 Complete the Chart Mass Number = 25 Enter the # of neutrons in clicker Your Turn: Number of Electrons Ex: Magnesium (Mg+2) # of protons = 12 # of electrons = 10 # of neutrons = 13 Mass Number = 25 Enter the # of electrons in clicker Welcome Back ! 1. Check Your Posted Grades Look at 2nd Marking Pd CLC’s and Verify Total Look at Separate CLC Gradesheet for 3rd MP 2. Pick up your “Clicker” and Log in. 3. Tell Your Lab Partner what “Mass Number” means 4. Enter in clicker the # of Neutrons that are in Mg-25 Welcome Back ! 1. Have you or your partner Log in to a nearby computer. 2. Ask your partner what “Atomic Number” means 3. Tell Your Lab Partner what “Mass Number” means 4. Enter in clicker the # of Neutrons that are in Mg-25 Warm-Up Ex: Magnesium (Mg+2) # of protons = 12 # of electrons = 10 # of neutrons = 13 Mass Number = 25 Enter the # of electrons in clicker Lesson Review 1. The _____ is the total mass of a single atom. A. B. C. D. Atomic Mass Mass Number Atomic Number Number of Protons Lesson Review 2. The _____ is always equal to the number of protons. A. B. C. D. Atomic Mass Mass Number Atomic Number Number of Neutrons Lesson Review 3. The _____ is equal to the number of protons and neutrons A. B. C. D. Atomic Mass Mass Number Atomic Number Number of Protons Lesson Review 4. The _____ is the difference between the number of protons and the number of electrons A. B. C. D. Number of Neutrons Atomic Number Mass Number Charge Time for Practice: • Log in to Moodle and go to the pHet Activity called “Build an Atom” • Choose Game at Level 4 Isotopes • Different “Varieties” of an Atom • Isotopes are atoms of the same element, but with different #’s of Neutrons. Therefore, they have different Mass #’s. • Isotopes are Chemically Identical • About 300 Stable Isotopes of the first 83 elements exist, plus several hundred more unstable isotopes Isotopes of Hydrogen: WhatWhat has to be the same for all will be different? three? 1 proton 0 neutrons Mass #: 1 amu 1 proton 1 neutron 2 amu’s 1 proton 2 neutrons 3 amu’s Isotopes of Have you ever heard Hydrogen: of “tritium” before? Hydrogen-1 Hydrogen-2 “Protium” “Deuterium” Mass Number 1 proton 0 neutrons Mass #: 1 amu 1 proton 1 neutrons 2 amu’s Hydrogen-3 “Tritium” 1 proton 2 neutrons 3 amu’s Isotopes of Hydrogen: Hydrogen-1 “Protium” Hydrogen-2 “Deuterium” 1 proton 0 neutrons Mass #: 1 amu 1 proton 1 neutrons 2 amu’s Hydrogen-3 “Tritium” 1 proton 2 neutrons 3 amu’s Naming Isotopes • The hydrogen isotope with 0 neutrons can be written as hydrogen-1 or 1H Mass Number 14 6 Number of Protons C How many Neutrons? Your Turn: Writing Isotopes How many of each particle are in this isotope: A 48 protons 51 electrons 124 neutrons B 51 protons 48 electrons 73 neutrons C 51 protons 51 electrons 124 neutrons 124 51 -3 Sb D 51 protons 54 electrons 73 neutrons Your Turn: Writing Isotopes • • • • The following element has how many 51 protons ______ 54 electrons ______ ______ 73 neutrons 124 -3 51 Sb Atomic Mass 1. Time for Grade Check 2. Look at your grade sheet and Calculate the Average of your grades for each unit 1. Is this your actual grade? 3. Grade = Unit1*(Weight) + Unit2*(Weight)…. Atomic Mass 1. Use this formula to calculate grade 2. Grade = Unit1*(Weight) + Unit2*(Weight)…. Atomic Mass • The AVERAGE mass of an atom of that element • Weighted according to the abundance of each Isotope • Ex: Football team Abundance of Hydrogen Isotopes: Hydrogen-1 “Protium” Hydrogen-2 “Deuterium” Hydrogen-3 “Tritium” Mass = 1 amu Mass = 2 amu Mass = 3 amu 99.985% 0.015% 1 x 10-16% Average Mass = 1.0079 amu = Atomic Mass Atomic Mass • The AVERAGE mass of an atom of that element • Weighted according to the abundance of each Isotope • Ex: Football team • Why are 99% of hydrogen atoms H-1? Pre-Knowledge Check • Get out your Atomic Structure Pre-Quiz and correct any incorrect answers you might have Alert: “ScienceStability Sense” Nuclear is Tingling • Rutherford says that nucleus is incredibly dense and small. • We now know that the nucleus consists of a bunch of individual protons • Nucleus consists of a bunch of protons crammed together in a tiny area Nuclear Stability • Protons Repel other protons. + + + • Putting Protons together in a tiny nucleus is unstable because of this repulsion • Neutrons act as “glue” to hold the protons together in the nucleus Stable Ratio of Neutrons to Protons • For smaller elements (1-30), about 1 neutron per proton seems to work best • 1:1 ratio Ex: Oxygen Protons = 8 Neutrons = 8 Most Stable Isotope has 1:1 Ratio Ex: Beryllium Protons = 4 Neutrons = 5 Most Stable Isotope has close to 1:1 Ratio Alert: “ScienceStability Sense” Nuclear is Tingling • Therefore, without this proper ratio of neutrons, the nucleus would be unstable and fly apart. So how can Hydrogen-1 exist as a stable atom? Ratio of Neutrons to Proton • As the elements get larger (>30), a higher ratio of neutrons is needed. • Example: Mercury has 80 protons, but around 120 neutrons are needed to hold them together • 120 / 80 is a 1.5 : 1 ratio. Your Turn: Predicting Stability 1. Who would more likely be stable? A. B. C. D. Phosphorous – 15 Phosphorous – 31 Phosphorous – 44 Phosphorous – 58 Protons 15 15 15 15 Neutrons 0 16 29 43 Your Turn: Predicting Stability 2. Who would more likely be stable? Protons Neutrons 0 74 A. 74W 74 76 B. 150W 110 74 C. 184W 74 151 D. 225W Radioactivity • After element # 83, the repulsive force of so many protons is so strong that no amount of neutrons will hold nucleus together permanently • Thus, no stable isotopes exist for these elements • These elements are called radioactive elements • The nucleus breaks apart and pieces of radiation come flying out Types of Radioactive Decay • Alpha Particle (α) – positively charged • Beta Particle (β) - negatively charged • Gamma Radiation (γ)- no charge Alpha (α ) Decay 240 Pu 94 236 U 92 + 4 He 2 Your Turn: Alpha Decay • Write down your description of what happens during alpha decay Beta (β ) Decay 228 Ra 88 228 Ac 89 + 0 e -1 Your Turn: Beta Decay • Write down your description of what happens during beta decay Gamma (γ ) Radiation • Gamma Radiation is NOT a particle • It is Electromagnetic Radiation given off during Alpha or Beta Decay Your Turn: Decay Equations • Write an equation of the alpha decay of Polonium-214 214 84 Po 210 82 Pb + 4 2 He • Write an equation of the beta decay of the Lead-210 210 Pb 82 210 Bi 83 + 0 e -1 Comparison of Radiation B o n e Skin Tissue Organs Your Turn: Radiation Comparison • Write a few sentences describing the penetrating ability and harmfulness of the three types of radiation Half-Life 16 1st half-life 5 seconds 8 5 seconds 2nd half-life 4 Red Balls have a 5 second half-life 3rd half-life 5 seconds 2 Half-Life • Add applications of half-life • Carbon-14 dating • Radioactive Waste • Assumptions & Limitations • Calibration and validation • Interpolating vs extrapolating • Other radiodating – age of the earth & universe Selected Answers to Page 11 & 12 1) nucleus 2) Strong nuclear 3) stable 4) Radioactive (unstable) 5) Mass 6) Nuclear (radioactive) 7) It can only be used to date organic things 9) Protons repel each other, so they would fly apart 14) 21084Po -> 20682Pb +42He 11) 42He 3 H -> 3 He +0 e 0 15) 1 2 -1 12) -1e 230 Th -> 226 Ra + 16) 90 88 13) 42He 4 He 2 14) 17) B 18) B Answers to Page 13 & 14 1) 0.0313 kg 3) 2.5 hr 5) 460 g 6) 7.81 g 8*) .0625 mol (don’t panic if you didn’t get this one) 2) 23,000 years 4) 90 years 7) 26 ug 9) 9 x 10-7 g 10) 160 sec. 238 1) Np 93 238 Pu 94 238 2) 92 U 234 Th 90 + + To Electrons 0 -1 e 4 2 He Nuclear Fission • Fission is when a large, unstable nucleus breaks apart into 2 similar-sized nuclei 235 1 + n U 0 92 94 139 + + Kr Ba 36 56 • Gives off a HUGE amount of energy! 1 3 0n Uses for Nuclear Fission • Atomic Bombs are an uncontrolled fission reaction • Nuclear Power plants use a controlled fission reaction • Energy produced by nuclear reactions is HUGE! • 1 Uranium pellet (2 oz) produces as much energy as: • 17,000 cubic feet of natural gas • 1,780 pounds of coal • 149 gallons of oil • A nuclear bomb can release about 1-20 million times more energy than the same mass of TNT Advantages of Nuclear Fission • The Good News! • Very efficient … a little bit of fuel makes a lot of energy • Nuclear Power Plants do not pollute! (No NOx, SOx, or CO2) • Reactors do not have enough uranium for an uncontrolled chain reaction. (subcritical mass) • They will never explode like a nuclear bomb Disadvantages of Nuclear Fission • The Bad News • Stuff left after fission reaction is unstable (“Dirty”) • Nuclear bombs affect area for miles around blast with radiation which takes decades to diminish • Radioactive Waste – • What do we do with it? • Dangerous for 1000’s of years • An accident could release radioactive material • Chernobyll • Reactor is housed in a containment unit to prevent this Why did Doc Oc want the tritium? Why did Doc Oc want the tritium? What is nuclear fusion? • Fusion is when 2 small nuclei combine to make a single, larger nucleus What is nuclear fusion? • Fusion reactions occur on stars (the sun) • This is source of energy given off by stars • Fusion rxns make new elements • H + H He Why the big deal over nuclear fusion? • Like fission, it produces lots of energy. (Even more per mass of fuel used) • Fusion would be MUCH SAFER than fission • Products are “clean” – not radioactive • Accidents are much less likely and less dangerous (it can’t meltdown) Are we close to using nuclear fusion? • Hydrogen Bombs use nuclear fusion (not dirty) • In over 50 years of trying, still no controllable production of energy by fusion • Since positively charged Wouldlike youcharges predictrepel, it to be easy or hard to fuse nuclei repel each other two nuclei together? Why? • Extremely high speeds are needed to overcome repulsion – Temperature must be 40,000,000 K Are we close to using nuclear fusion? • High temps would obliterate anything used to try to contain the reaction (metal, concrete walls) • Can use high-powered lasers to try to get up to extremely high temperatures • Tokamak – device that uses a magnetic field as the “wall” to try to contain the reaction Joint European Torus (JET) Tokamak in Oxfordshire, UK Are we close to using nuclear fusion? • Reactors do exist, but currently use more energy than they produce. • Hopefully by 2010 we will “break even” • Possible major source of power in world by 2050 Revision: Law of Conservation of Matter and Energy • During both fission and fusion, Mass IS LOST • The mass that is lost is transferred into HUGE amounts of energy (E=MC2) • One little pellet of Uranium can produce as much energy as 2000 pounds of coal • This is why nuclear reactions give off such a HUGE amount of energy – lost mass changes into energy! Time to Check HW Things Associated with Nuclear Chemistry Mass Number Nuclear Fission Beta Decay Ion Atomic Mass Plum Pudding Model 98 Things Associated with Nuclear Chemistry Alpha Particle Half-Life Isotope Atomic Number Ground State 1.5 to 1 Ratio 99 Understanding the Motion of Electrons • Do electrons just randomly move about the nucleus? • If so, they could possess any given energy at any given point in time Story of Trumpet & Guitar Max Planck & The PhotoElectric Effect • When some metals are exposed to certain wavelengths of light, the electrons absorb the energy and are emitted. Other wavelengths of light show no effect Page 18B Story of Trumpet & Guitar Max Planck & The PhotoElectric Effect This seemed to indicate that electrons in the atoms possessed specific energies and not just any random amount of energy. Bohr Model of Atom (The Solar System Model) 1 2 3 • Electrons “orbit” the nucleus in fixed, quantized energy levels • Electrons exist only on these energy levels • Electrons can “jump” up energy levels if a matching photon of energy is absorbed (excited state) Bohr Model of Atom (The Solar System Model) 1 2 3 • Electrons can “jump” up energy levels if a matching photon of energy is absorbed (excited state) • Electrons give off energy when they “jump” back down to the more stable ground state. • Ground State – when the electrons in an atom are arranged in the lowest possible energy level. • Further Evidence for Bohr Model • When heated, each element emits energy in certain wavelengths (neon lights) -- demo • These energies given off can be separated by a spectroscope producing a line spectra Lithium • Each line a specific amount of energy with a specific wavelength • Each line represents a specific jump that an electron is making within that atom • Each element has energy levels in different places, so they have different ‘jumps’ • Each element produces its own unique spectrum Sodium Mercury Lithium Hydrogen Atomic Line Spectra • Spectrum are often called the “fingerprint” of an element • Use spectra to determine what gases are in stars • Demo – flame test Jumping of Electrons Show possible jumps for Elliot This chart shows all the possible jumps an electron of hydrogen can make Each jump produces a specific amount of energy with a specific wavelength Each arrow represents a jump an electron can make Energy Level #3 Energy Level #2 This arrow represents an electron jumping from level 3 to 2 Each arrow represents a jump an electron can make Energy Level #3 Energy Level #2 This jump is labeled “a” in the “Balmer Series” Each jump produces a specific amount of energy with a specific wavelength 500 400 e d c b 600 700 a Hydrogen Balmer Series An electron jumping from level 3 to 2 will always give off energy with a wavelength of 650 nm (red light) “a” in the “Balmer Series” Warm-Up: Turn to page 28 in your packet and determine the wavelength of the energy produced when a hydrogen electron jumps from energy level # 6 to 3 B) If 1 Angstrom = 1 x 10-9 m, what is this wavelength in meters? What jump makes this blue? 500 400 e d c b 600 a Hydrogen Balmer Series 700 Page 28 – jumps of hydrogen • HW – Page 29 Quantum Mechanical Model Our Modern View of the Atom Bohr Model vs Quantum Model The electrons do not travel in fixed paths as Bohr suggested, however their motion is not entirely random either. The electrons have regions where have high probabilities of being found Space Orbital - area where an electron will be within 90% of the time. Quantum Numbers The 4 Quantum Numbers are like an “address” describing the location of an electron No two electrons have the exact same set of quantum numbers Principal Quantum Number (n) Describes the energy level that electron is in Energy level represents average distance an electron is from nucleus The larger the energy level, the larger the orbital and farther away from nucleus electron is 12 3 Angular Quantum Number (l) Sometimes called “Orbital” or “Azimuthal” Q.N. Describes which type of orbital electron is in. Orbitals are defined by their shape. Book page 142….. S orbitals (l=0) Shaped like a sphere or ball Only 1 present in each energy level P orbitals (l=1) Shaped like an hourglass, dumbbell, peanut “P’s come in 3’s” -- have three on an energy level D orbitals (l=2) Four leaf clover shaped, Daisy, “Double-peanut” How many? 5 on an energy level. F orbitals (l=3) Too complex and variable to visualize shape How many? 7 Magnetic Quantum Number(ml) Tells which “p” orbital electron is in. Named according to axis they are oriented along. Py Px Pz Spin Quantum Number(ms) Each orbital can hold up to 2 electrons 2 Electrons may occupy the same orbital only if they are spinning in opposite directions. +1/2 (or 1) - first electron in orbital -1/2 (or -1) - second electron in orbital “+” and “-” indicate direction, NOT CHARGE Learning Check Give the quantum numbers for the second electron placed in a dumbbell-shaped orbital in the horizontal position in the 4th energy level. Orbitals & Energy Levels Not every energy level has every orbital: Energy Level Orbitals Present Max eCapacity 1 s 2 2 s,p 8 3 s,p,d 18 4 s,p,d,f 32 HomeWork – due tomorrow Complete Page 21 & 22 Complete Pages 14B & 14C Orbital “Order of Filling” Shortcut Electron Config Looking at the Pd Table s1 (special no rule-breaker version) p1 p2......... s2 s-Block d1 d2 d3 d4* d5 d6 d7 d8 d9* d10 p-Block d-Block p6 Looking at the Pd Table s1 p1 p2......... s2 s-Block d1 d2 d3 d5 d5 d6 d7 d8 d10 d10 p-Block d-Block p6 Your Turn: Shorthand Config • Do Shorthand Electron Configuration for: • Sr • Mo • Sb 3. Electron Dot Notation • • • • Electron dot notation shows only outer shell (valence) e’s Valence electrons are the outermost electrons in an atom – or - the electrons in the highest energy level Example: Oxygen 1s22s22p4 6 valence electrons Outer Shell What’s the highest energy level that has e’s How many valence e’s 3. Electron Dot Notation Inner Shell 4 valence electrons • Example: Ge 1s22s22p63s23p64s23d104p2 Outer Shell Can d orbital electrons ever be in the outer shell? What’s the highest energy How many level that has e’s e’s valence Electron Dot Notation • Only s and p electrons can ever be in outer shell 8 electrons to fill the outer shell • It takes __ • A filled outer shell is called an octet • An octet is the most stable configuration an atom can have What elements • Noble Gases have octets have octets? 1 2 # of valence e’s 3 4 5 6 7 8 How many valence e’s does sulfur have? Electron Dot Notation S How many valence electrons? S 3s 3p Electron Dot Notation Unpaired electron S Electron Pair Electron Dot Notation 5 7 4 8 X 6 3 1 2 Your Turn: Electron Dot • Do the electron dot notation for the elements listed on the top part of page • Also – tell how many pairs and unpaired electrons each element has The following slides are generally not covered in CP Chem Don’t worry about the following unless instructed to. Order of Filling “Rule Breakers” The Reasons: Having a filled energy level is a very stable configuration (Noble Gases) Ne 2s 2p Having a filled subshell is also extra stable Mg 3s 3p Having a half-filled subshell is also a bit extra stable P 3s 3p Order of Filling “Rule Breakers” Who breaks the rules? Elements whose last d and f orbitals are 1 electron short of being filled or half filled 4s 4s 3d Almost Filled 3d Almost Half- Filled Order of Filling “Rule Breakers” What do they do? An electron is moved from the higher ‘s’ orbital and placed in the d orbital to fill or half-fill it 4s 4s 3d 3d Filler Half-Filler s and p orbitals do not do this. The energy difference between them is too great. (see poster) Order of Filling “Rule Breakers” Bottom Line: You will never have a final answer with d orbitals looking like this: Or this: 5s24d9 5s14d10 5s24d4 5s14d5 Order of Filling Rule Breakers Go to Your Homework Identify any rule-breaker Write the correct configurations in