Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* How can we describe an atom? How can atoms of the same element be both similar and different at the same time? What do we call an atom that is not neutral? How can we calculate the average mass of isotopes? How has the model of the atom evolved over time? How can we describe the modern model of the atom? How can we describe where are electrons are located within the electron cloud? How can we describe how electrons are arranged? What is electromagnetic radiation? How is light produced? - Honors Chemistry AIM: How can we describe an atom? The Theory of the Atom • ________________, a famous Greek teacher who lived in the 4th Democritus Century B.C., first suggested the idea of the atom. • ________ John __________ Dalton came up with his atomic theory based on the results of his experiments. The Atom • element The smallest particle of an ________________ is an atom. • subatomic The atom is made up of three ________________ particles. 1897 by J. J. Thomson by using (1)The electron was discovered in _______ (−) charge. It’s mass a cathode ray tube. The electron has a _______ is much smaller than the other 2 subatomic particles, therefore ignored it’s mass is usually ______________. *Cathode Ray Tube (+) (2) The proton has a ______ charge, and it was discovered in 1886 _________ by E. Goldstein. (3) The neutron does not have a charge. In other words, it is neutral It was discovered in 1932 ________. ____ by James Chadwick. The mass as the proton. neutron has about the same _________ visible matter *These three particles make up all the ____________________ in the Universe! *There are other particles such as neutrinos, positrons, and quarks, but are typically left for 2nd year chemistry courses. Nuclear Atomic Structure *The atom is made up of 2 parts/sections: (1) The ______________ --- (in the center of the atom) nucleus electron _________ cloud --- (surrounds the nucleus) (2) The ____________ (p+ & n0) e− cloud The Nucleus Rutherford in ________. 1911 *Discovered by Ernest ________________ *He shot a beam of positively charged “alpha particles”, helium nuclei, at a thin sheet of ______ gold foil which are ___________ _____. • 99.9% of the particles went right on detector through to the ______________. * • Some were slightly deflected. Some bounced back even ____________ ________ towards the source! • This would be like shooting a cannon ball at a piece of tissue paper and having it bounce off. * Rutherford’s Experiment * Conclusions about the Nucleus (1) Most of the atom is more or less _________ empty ___________. space tiny (2) The nucleus is very _________. (Stadium Analogy) dense (3) The nucleus is very ___________. (Large Mass ÷ Small Volume) positively (4) The nucleus is ______________ charged. Counting Subatomic Particles in an Atom protons • The atomic # of an element equals the number of ____________ in the nucleus. protons • The mass # of an element equals the sum of the _____________ and neutrons ______________ in the nucleus. electrons • In a neutral atom, the # of protons = # of ______________. subtract • To calculate the # of neutrons in the nucleus, ______________ the atomic # from the __________ mass ___________ #. * (1) Practice Problems Find the # of e-, p+ and n0 for sodium. (mass # = 23) Atomic # = 11 = # e- = # p+ 2) # neutrons = 23-11 = 12 Find the # of e-, p+ and n0 for uranium. (mass # = 238) Atomic # = 92 = # e- = # p+ # neutrons = 238-92 = 146 3) What is the atomic # and mass # for the following atom? # e- = 15; # n0 = 16 Atomic # = 15 = # e- = # p+ Mass # = p+ + n0 = 15+16 =31 The element is phosphorus! * REMEMBER P….E….N Element Name Symbol Atomic # AMU # of Protons # of Electrons K 19 # of Neutrons 19 5 16 23 10 48 25 14 14 *AIM: How can atoms of the same element be both similar and different at the same time?- Isotopes * Isotopes *An isotope refers to atoms that have the same # of ___________, protons neutrons but they have a different # of ___________. mass #’s (or simply, *Because of this, they have different _________ masses different ___________.) *Isotopes are the same element, but the atoms weigh a different neutrons amount because of the # of ______________. Examples---> (1) Carbon-12 & Carbon-13 (2) Chlorine-35 & Chlorine-37 (The # shown after the name is the mass #.) atomic *For each example, the elements have identical ___________ #’s, mass #’s, (# of n0). (# of p+) but different _________ *Another way to write the isotopes in shorthand is as follows: 12 6 C 35 17 Cl mass #, and the bottom # is the __________ atomic The top number is the ________ subtracting number. Calculating the # n0 can be found by _____________ the #’s! * Figure 3.10: Two isotopes of sodium. * More Practice Problems (1) Find the # e-, p+ and n0 for Xe-131. Atomic # = 54 = p+ = e− 2) Find the # e-, p+ and n0 for n0 = 131 − 54 = 77 63 29 Cu Atomic # = 29 = p+ = e− n0 = 63 − 29 = 34 3) Write a shorthand way to represent the following isotope: # e- = 1 # n0 = 0 Atomic # = p+ = e− = 1 H-1 or # p+ = 1 mass # = n0 + p+ = 1+ 0 = 1 1 1 H * Atomic Mass 12 *Based on the relative mass of Carbon-12 which is exactly _______. *1 p+ ≈ __1 atomic mass unit (amu) 1 n0 ≈ __1 amu 1e- ≈ __0 amu *The atomic masses listed in the Periodic Table are a “weighted average” of all the isotopes of the element. Weighted Average Practice Problems: (1) Mrs. Smith’s geometry semester grades are calculated using a weighted average of three category scores: Major Grades= 60% of your grade Minor Grades= 30% of your grade Semester Exam=10% of your grade • If a student had the following scores, what would they receive for the semester? Major= 80 (B − ) Minor= 60 (D −) Semester Exam=65 (D) * Weighted Average Step (1): Multiply each score by the % that it is weighted. Step (2): Add these products up, and that is the weighted average! 60% x 80 = 48.0 30% x 60 = 18.0 + 10% x 65 = 6.5 72.5 (C−) Add them up!! A “normal average” would be calculated by simply adding the raw scores together and dividing by 3… 80 + 60 + 65 = 205 ÷ 3 = 68.3 = D * Average Atomic Mass Practice Problems: (2) In chemistry, chlorine has 2 isotopes: Cl-35 (75.8% abundance) Cl-37 (24.23 % abundance) What is the weighted average atomic mass of chlorine? 35 x 0.758 = 26.53 + 37 x 0.2423 = 8.9651 35.4951 amu Add them up!!! (3) Oxygen has 3 isotopes: O-16 (99.76%) O-17 (0.037%) Estimate oxygen’s average atomic mass. Barely over 16.0 amu O-18 (0.2%) * Average Atomic Mass (4) Copper has an average atomic mass of 63.546 amu. It contains only two natural isotopes, which are Cu-63, with an isotope mass of 62.940 and Cu-65 with an isotope mass of 64.928. What are the percent of the two isotopes in naturally occurring copper? Avg. Atomic Mass = (%Cu-63 x Mass Cu-63) + (%Cu-65 x Mass Cu-65) % Cu-63 + % Cu-65 = 100% OR % Cu-63 + % Cu-65 = 1 63.546 = (%Cu-63 x 62.940) + (%Cu-65 x 64.928) * 1. 80% 2. 127I, 17% 126I, 3% 128I 50% 197 Au, 50% 198 Au * Nucleons: particles in the nucleus (protons and neutrons) Nuclear Charge: charge of the nucleus (same at # of protons) Examples: 1. How many nucleons are there in an atom with an atomic number of 20 and 23 neutrons? 2. What is the nuclear charge of an Iron atom? * * * Ions An atom can gain or lose electrons to become electrically charged. + charged atom created by ___________ losing e-’s. Cation = (___) * * * Cations are ______________ than the original atom. smaller _____________ generally form cations. Metals Anion = (___) e-’s. − charged atom created by _____________ gaining * * larger Anions are ____________ than the original atom. _______________ generally form anions. Nonmetals Practice Problems: Count the # of protons & electrons in each ion. a) Mg+2 12 10 p+ = _____ e− = ______ b) F−1 9 10 p+ = _____ e− = ______ * AIM: How has the model of the atom evolved over time?- Modern Atomic Theory\ Atomic Models (1) • • • Thomson a ball of (+) charge containing a number of enucleus no ________________ plum pudding often described as the “________ _______________” atom. Rutherford (2) • • Model: Model: nucleus a ____________ of (+) charge surrounded by a number of eneutrons no _____________ and no e- orbitals Atomic Models Bohr (3) • • • • Model: neutrons a nucleus of (+) charge that also contains ______________ nucleus is encircled by e-’s located in definite orbits (or paths). fixed e-’s have ___________ energies in these orbits e-’s do not lose energy as they orbit the nucleus Quantum Mechanical Model ( Wave Mechanical Model) (4) • • shape no definite ____________ to the e- path (“fuzzy” cloud) probability orbits of e-’s based on the _________________ of finding the e- in the particular orbital shape. * Bohr Atomic Model http://www.slideshare.net/laburkett/history-of-the-atom * *Heisenberg showed that the more precisely the momentum of a particle is known, the less precisely is its position known: h (x) (mv) 4 *In many cases, our uncertainty of the whereabouts of an electron is greater than the size of the atom itself! * * Quantum Mechanical Model AIM: How can we describe where electrons are located? - Energy Levels Diagram: • The energy levels in an atom are rungs of a ladder. sort of like _________ • The more energy an electron has, the __________ farther away from the nucleus it usually will be. • The energy levels are not evenly spaced. They get ___________ closer together as you travel farther away. • To move from one “rung” to quantum another requires a “____________” of energy. * continuous energy levels quantized energy levels * Quantum Numbers location *Describe the ______________ of the e-’s around the nucleus. address *Quantum #’s are sort of like a home _____________ for the electron. *This information about the location of the e-’s in an atom can be used to: properties for the (1) determine chemical & physical _____________ elements. Periodic Table is organized. (2) show how the _______________ __________ how and _____ why elements combine to form (3) show _____ compounds. * The Four Quantum Numbers 1. Principal Q. #: Describes the _____________ distance that the electron is from the nucleus. The bigger the number, the farther away the electron is. ___________ Example: (1=closest, 2, 3, 4...farther away) principal These distances are sometimes called _______________ energy levels ______________ ____________. 1 2 3 nucleus 2. shape Orbital Q. #: Describes the __________ of the electron’s path around the nucleus with a letter: (s, p, d, & f) These are sublevels sometimes called “_____________”. spherical cloud; s=_____________ ellipsoid p=_____________ or a 3-D figure 8; * * d & f orbital shapes are criss complex ________crossing _______________ ellipsoids, and some d’s and f’s are an ellipsoid with a doughnut or two around the middle. All of these orbital shapes are based on the probability of finding the electron in the cloud. f - orbitals d - orbitals * s p d s p f d s p s * 1 sublevel 2 sublevels 3 sublevels 3. Magnetic Q. #: tells how many _________________ orientations in 3-D there are about the nucleus for each orbital shape. s=___ 1 orientation 3 orientations... (x, p= ___ 5 orientations d= ___ 7 orientations f= ___ y, and z) *The orientations are represented with a line or a box. Examples: ___ distance of 1s orbital is spherical orbital at a This means a __________ “__” (close) to the nucleus. This 1 centered about the x, y, and z axis. □□□ orbital with its 4 distance of “___” 4p ellipsoid This represents an ___________ ____ 3 possible orientations at a from the nucleus. * 4. Spin Q. #: describes how the electron in an orientation is spinning up or around the nucleus. This spin can be thought of as “____” down “________”. (Some like to imagine it spinning “clockwise” and arrow “counterclockwise”.) The spin is represented as an ___________ in the direction of the spin. spherical _________ distance of Example: ↑ This represents one electron in a up 2s orbital with spin “____” at a “___”from the nucleus. 2 *Remember, the four quantum numbers tell us the location, or “address” of each electron in an atom. *This information is vital in understanding the layout of the Periodic Table and the reasoning behind why and how atoms form bonds. AIM: How can we describe how electrons are arranged? - Electron Configurations * Electron configurations are notations that represent the four Quantum #’s for all of the electrons in a particular atom. Here are the rules for these notations: *Rule #1 (Aufbau Principle): Electrons fill ________ lowest energy orbitals first. Examples: 2s 1s would be filled before ____ 3p 3s would fill before ____ Electron Configurations Silicon ↑ ↑ ↑↓ ↑↓ ↑↓ ↑↓ ↑↓ (Energy Level Diagram) ↑↓ 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p… *Rule #2: Only ___ 2 electrons can fit into each orientation. Example: ___ ↑↓ 1s ___ ↑ 2s not ____ ↑↓↑ 1s *Rule #3 (Pauli Exclusion Principle): Electrons in the same opposite orientation have ______________ spin. Example: ↑ ↓ not ___ ↑↑ ___ 1s 1s *Rule #4 (Hund’s Rule): □ Monopoly “_______________ rule”---> Every “ ” in an orbital shape gets an electron before any orientation gets a second e-. Example: □□□ ↑ ↑ 2p ↑ not 2p □□□ ↑↓ ↑ *Rule #5: * The Exceptions lower Half-filled or completely filled d & f sublevels have ________ energies and are more stable than partially filled d’s and f’s. * This means that an atom can “borrow” one of its “s” electrons from the previous orbital to become more stable. Example: ↑↓ ___ 5s becomes ↑ ↓ ___ ↑↓ ↑↓ ↑↓ ↑ ___ ___ ___ ___ 4d ↑↓ ___ ↑ ↑↓ ↑↓ ↑↓ ↑↓ ___ ___ ___ ___ ___ 5s 4d lower * Because the 4d sublevel is now full, the atom is at a ________ more stable. energy state and therefore _________ Electron Configurations ↑ ↑ ↑↓ Silicon ↑↓ ↑↓ ↑↓ ↑↓ (Energy Level Diagram) ↑↓ 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p… * Electron Configurations Practice Problems: Write the electron configuration notation for each of the following atoms: *Hydrogen *Carbon *Iron *Bromine Shorthand Method: Assumes we already know about the # of *H *C *Fe *Br □. * How Electron Configurations Relate to the Organization of the Periodic Table s p d f * * Electron Configurations & Properties *How do electron configurations relate to the chemical and physical properties of an element? same outer shell e- configurations have *All elements with the _________ ________ similar properties. vertical *This means that elements in the same ____________ group have similar properties. s Examples: (1) Li, Na, K, Rb, and Cs all have __1lone “__” e- for their last orbital... (_____, 2s1 _____, 3s1 _____, 4s1 etc.) This makes all of very water to them ___________ reactive. They all react with __________ produce hydrogen gas. (2) Ne, Ar, Kr, Xe, and Rn all have the outer energy level filled 2s2 2p6 3s2 3p6 completely __________ with electrons...(________, ________, 4s2 4p6 etc.) This makes all of them ______________. inert ________, They do not produce __________________! compounds More Practice Problems Bromine (1) Which element has its last electron as a 4p5? ___________ F, Cl, I, At (2) Which elements are similar in properties as Bromine? __________ (3) What would the outer shell electron configuration look like for the element underneath Radon, (Rn)? …7s2 5f14 6d10 7p6 4f1 (4) Which electron is added after 6s2? ________ (5) Which element would “borrow” a 5s electron to get a half-filled Mo “d” sublevel? ___________ (6) What is the shape of the last orbital filled in Calcium, (Ca)? sphere _____ (7) How many electrons are in the last “p-orbital” of Sulfur, (S)? 4 ____ * Electromagnetic Radiation *Any wave of energy traveling at a speed of ___________ light is called electromagnetic radiation. *There are many types of electromagnetic radiation and each type has a different _______________ and _______________. frequency wavelength *Here are the types of electromagnetic radiation from longest to shortest wave or lowest to highest frequency. These are also in order from lowest to highest energy. * Electromagnetic Radiation * AIM: What is Electromagnetic Radiation? (1) Radio Waves -- used in __________________ communications cook _______. food (2) Microwaves-- broadcasts TV signals and used to _____ heat _________ Snakes & ______ owls can (3) Infrared (IR) -- we feel this as _____; “see” this. infrared image of a cat infrared image of heating pipes under a floor * Infrared Vision * Electromagnetic Radiation (4) Visible Light -- the only radiation we can detect with our eyes. It prism can be separated into the colors of the spectrum with a __________. ROYGBIV sunburn Bees (5) Ultraviolet (UV) -- gives you a _____________; _________ can “see” this; some of this radiation from the sun gets blocked by the ozone ___________ layer flower photo under normal light flower photo under UV light * Electromagnetic Radiation (6) X-rays -- used in medicine Ouch! * Electromagnetic Radiation (7) Gamma Rays-- some radioactive substances give it off Cosmic *_______________Rays – These are not part of the EM spectrum… They are high energy particles (mostly protons); They cause the northern lights. Interesting superhero facts: • Superman has x-ray vision. • The Incredible Hulk was “created” by an accidental overdose of gamma radiation. • The Fantastic Four were “created” by cosmic rays. * How Light is Produced *When atoms get hit with zapping energy (by _____________ them with electricity or by heating them up), the ____________ electrons absorb this energy and __________ jump to a higher energy level. Figure (a) *As they immediately fall back down to the “____________ ground state”, they give off this energy in the form of a particle light (or other of ___________ types of electromagnetic radiation)photon called a _____________. Figure (b) * How Light is Produced *Each photon emitted has a color specific ___________ (or frequency). *The color of the light that is given off depends on how far the electron _______ fell _____ (which depends on how big of a jump it originally made.) The farther the fall, the greater energy the ___________ photon has. * * How Light is Produced energy levels (or *Since electrons are located only in certain __________ orbitals) around the nucleus, only certain specific _________ color of light are emitted. spectroscope *Scientists use a _________________ to separate these colors into bar code of color bands of light. These bands of color look like a ______ which is characteristic of that element. No two elements produce the spectrum same ______________ of colors. This can be used to distinguish one element from another contained in a sample. (See Fig. 13.11) * Emission Spectrum Hydrogen Spectrum Neon Spectrum * Measuring the Energy of Photons *The photons of light given off or absorbed by atoms have specific energies that can be calculated according to the following formula: E=hν (E = h f…some textbooks write it this way.) E = energy (in joules) h = Planck’s constant = 6.63×10−34 J·s ν (nu) = frequency of the light in units of Hertz (waves per second)…s-1 *The frequency of light can be determined if given the wavelength (in meters) according to the following formula: c=λν (c = f λ…some textbooks write it this way.) c = the speed of light = 3.0 x 108 m/s λ (lambda) = wavelength (in meters) Both of these equations are given to you on the AP Equation Sheet. How hydrogen produces the four visible photons All the Photons Produced by Hydrogen * * Louis de Broglie suggested that if light can have material properties, matter should exhibit wave properties. * He demonstrated that the relationship between mass and wavelength was * h = Planck’s constant and v = velocity * Quantity mv is called its momentum h = mv * http://www.brainpop.com/science/matterandchemistr y/atomicmodel/