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Download Chemistry 1st Grading Period Notes 090211 Pointers Topics Identify
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Chemistry 1st Grading Period Notes 090211 Pointers Topics 1. Identify the Aspect of Matter and Branches of chemistry being described in a statement 2. Scientific Measurement - Read and create calibrations - Identify no. of significant digits - Round of to significant digits - Use scientific notation - Assess measurements SD - Percentage Error 3. Atomic Structure - Scientists who contributed to the development - Experiments done - Facts about subatomic particles - Atomic models 4. Atomic Parameters - Know how to get the: atomic weight, atomic number, proton, electron, neutron, and charge of atoms, ions, and isotopes 5. Relative Atomic Weight 6. Quantum number - Determine quantum numbers - Identify elements using Quantum numbers - Evaluate if a set of Quantum numbers is valid or invalid 7. Electronic Configuration - Shell configuration - Box configuration 8. Sig. Contribution of Scientists Type of Tests 1. True or False (15) 2. Multiple Choice (30) 3. Matching Type A (10) Scientists, experiments, and contributions 4. Matching Type B (5) Calibration 5. Problem solving (20) RAW, Percentage Error, SD 6. Essay (5) 7. Table Completion (15) ASPEN and Quantum numbers I. Chemistry as the study of matter Study of matter- matter: takes up space and has mass Central Science Pure Substance vs. Mixture Pure Substance- chemically combined, has a fixed ratio Elements- 1 atom, ex: gold, oxygen Compounds- 2 or more atoms, ex: water, carbon dioxide II. Mixture- physically combined Homogenous- cannot distinguish, ex: salt and water mixture Heterogeneous- can distinguish, ex: salad mixture Aspects of Matter Changes- response to a reaction; to form; to create, ex: Fe+ 02 -> Fe203 Composition- elements present or found in a piece of matter Quantitative Analysis- specific, numbers Qualitative Analysis- general, traits (5 senses) Application- how is it used and how is it beneficial Laws and Principle- reason behind the change of observation, ex: Aufbau’s Principle, Charles Law, Boyles Law, Dalton’s Atomic Theory, Octet Rule Characteristics- structure and form Physical Properties- can be identified without altering the identity of the substance Chemical Properties- can be identified in chemical reactions Extensive Properties- depend on the amount of matter present, ex: mass, weight, volume, length Intensive Properties- do not depend on the amount of matter present, ex: color, luster, ductility, hardness, boiling point, odor Structure- how atoms and molecules form and shape (shape is governed by how many bonding pairs there are around the central atom, and by how many of those pairs are participating in a bond) Valence- shell- electron- pair- repulsion model (VSEPR)- a model that states electron pairs in a molecule will be as far apart from one another as they can be because they repel each other Branches of Chemistry Organic Chemistry The Science of designing, synthesizing, characterizing, and developing applications for molecules that contain carbon (6th element) Study about medicine, food, create and study organic compounds Work in and outside the lab Work in modern, clean, well lighted, and safe research or development facilities equipped with up to date equipment and instrumentation Employed by pharmaceutical, biotechnical, chemical, consumer product, and petroleum corporations III. Traits- creativity, technical, problem solving, unity Carbon Dating- discovering how long a living organism lived; half life- how long it will disappear in Analytical Chemistry Science of obtaining, processing, and communicating information about the composition and structure of matter Art and science of determining what matter is and how much of it exists Perform qualitative and quantitative analysis Science of sampling, defining, isolating, concentrating, and preserving samples Create new ways to make measurements, interpret data in proper contest and communicate results Biochemistry Study the structure, composition, and chemical variations of substances in living systems Is applied to medicine, dentistry, and veterinary medicine Work in the field is often related to toxology Biochemist- works in modern research laboratories, employed as teachers or researchers in schools of arts and sciences, in government agencies such as Department of Agriculture, the National Institutes of Health and Environmental Protection, and Drug Pharmacies Inorganic Chemistry Study of the synthesis and behavior of compounds not containing carbon Studies behavior and analogues for inorganic elements and how these materials can be modified, separated or used in product applications Employed in mining Physical Chemistry Study of the molecular and atomic level of how materials behave and how chemical reactions occur Physical chemists develop theories about these properties, and analyze materials and discover potential use for materials Scientific Measurement Measurement Represents Quantities Contains a number and a unit Scientific International (SI) Measurement Developed by the Chemist Lavoisier Multiple and submultiples of metric units are related by powers of ten The names for these are formed with prefix Nano, Micro, Mili, Centi, Deci, Deca, Heca, Kilo, Mega, Giga, Tera SI Base Units- one, ex: cm, m, mL SI Derived Units- combined, ex: density, kmph, g/mL Reading Calibrations Measuring Devices are calibrated with lines and numbers Calibrations- set a limitation on an instrument’s capacity to measure Read specific place values with certainty and estimate one place value Accuracy- smallest line which can be accurately measured Sensitivity- estimated value Rules for determining significant digits 1. 2. 3. 4. 5. 6. All nonzero digits are significant: ex: 999- 3 SD Sandwich rule- if it’s between two nonzero digits, it’s significant: ex: 9003- 4SD If it has a barline, it’s significant- 500- 3 SD Zero to the right of a nonzero digit and a decimal point is significant: ex: 5.00- 3 SD Zeros between a nonzero digit and a decimal point is significant: ex: 7000.0- 5 SD Exact numbers- number or unit not take from a measuring device have infinite significant digits: ex: 30 students, 6 innings Rules for rounding off 1. 2. If the last decimal place is lower than 5, do not round up. Ex: 42. 236 m – round off to 3 SD – 42.2 m If the last decimal place is 5 or more, round up Ex: 2.65465 m – round off to 2 SD – 2.7 Scientific Notation m x 10n Scientist’s way of expressing very big and very small numbers m= 1 < n < 10, n= # of times the decimal point was moved n= + if the original value is more than one n= = if the value is less than 1 ex: 560,000 m= 5.6x 105 E= sum x= single measurement n= # of measurements x= mean (average) Ex: 1 x 24.06 g x-x -3.18 (x-x)2 10.1124 Solving Equations Initial answer- raw answer Final answer- rounded off Addition and Subtraction- round off to the least number of decimal places Ex: 52.13g + 1.7502g IA: 53.8802 g; FA: 53.88 g Multiplication and division- round off to the least number of significant digits Ex: 6.41 m x 12 m IA: 76.92 m2; FA: 77 m2 Significant Numbers in Calculations A calculated answer cannot be more precise than the measuring tool A calculated answer must match the least precise measurement Significant Figures are needed from Final Answers from: Adding and Subtracting and Multiplying and Dividing Assessing Data Accuracy- how close the measurement is to the true value Precision- how close the measurements are to each other Percentage Error Error= | Theoretical value – Experimental value| Percentage Error= |Theoretical value – Experimental value (x100%)| / Theoretical value 2% or above= not accurate Ex: Average= 25.50, Real= 25.40 Error= -.10 cm or 10 cm Percentage Error= -.39% Standard Deviation Used to measure precision The lower the SD, the more precise the measurement SD= sqrt E (x- x) 2/ n-1 2 3 28.09 g .85 .7225 29.56 g 2.32 5.3824 m=27.24 g E= 16.2173 Comments: Poor Accuracy, Poor Precision %E= |25.1127.24| / 25.11 x 100 = 8.483% SD= sqrt 15.2173/ 3-1= 2.8 g IV. Atomic Models Democritus Atomos (uncut, undivided) Reasoned that if you continued to cut a stone you would reach a piece so small and miniscule it would not be able to be divided John Dalton Father of Modern Atomic Theory Revived and revised Democritus’ ideas based upon the result of a scientific research he conducted The solid, indivisible sphere Joseph John Thomson Discovered the electron in a series of experiments designed to study the nature of electric discharge in a high vacuum cathode- ray tube Plum pudding model, raising bread model, chocolate chip model= Cathode Ray Experiment Ernest Rutherford Described the atom as having a central positive nucleus surrounded by negative orbiting electrons Mass of the atom was contained in the small nucleus and that the rest of the atom was mostly empty space Gold Foil Experiment- Nuclear Model of the Atom Niels Bohr Electrons can occupy certain orbits or shells in an atom. Each orbit represents a definite energy for the electron in it Light is emitted by an atom when an electron jumps from one of its allowed orbits to another Since each orbit represents definite electron energy, this electron jump, or transition, represents definite energy jump. This change in electron energy leads to emission of light of a definite energy or wave length Planetary Model, Solar system Model The Bohr model consists of four principles 1. Electrons assume only certain orbits around the nucleus. These orbits are stable and called “stationary” orbits 2. Each orbit has an energy associated with it. For example the orbit closest to the nucleus has an energy E1 the next closest is E2 and so on. 3. Light is emitted when an electron jumps from a higher orbit to a lower orbit and absorbed when it jumps from a lower to higher orbit 4. The energy and frequency of light emitted or absorbed is given by the difference between to orbit energies ex: E (light) = Ef- Ei n= E (light)/ h h= Planck’s constant = 6.627x 1032 Wave Mechanical Model Based on the particle and wave nature of the electron Based on the probability of where electrons are going to be at a point in time Schrodinger wave equation relates kinetic energy and potential energy to the total energy, and it is solved to find the different energy levels of the system Orbits- orbitals (spdf or spaces) Heisentbergs uncertainty principle The more precisely the position is determined, the less precisely the momentum is known in the instant and vice versa Impossible to know the exact location and speed at the same time Uncertainty Paper- 1927 Isotopes- same atomic number, different atomic mass Alpha particles- positive, nucleus- positive= they repel Eugene Goldsteinconducted the same experiment as JJ Thomas with Canal Rays and discovered the Protons JJ Thomson- Electron Ernest Rutherford- Nucleus James Chadwick- Neutron V. Atomic Parameters (A, Z, p+, e-, no) Atomic Weight (A) Based in comparison with carbon 12 Carbon 12- 12 g- 6.02x 1023 atoms Weights= 1 mole of atom= 6.02x 1023 atoms Proton+ Neutron Atomic number (z) Equal number of protons Positively charged particle 1.602 x 10-19 Conlomb (c) Electron (e-) Negatively charged 1.602 x 10-19 Conlomb (c) Robert Millikon discovered the charge and mass of an electron Electrons were discovered by JJ Thomson in his research with cathode ray tubes Robert Millikan calculated the electron’s mass in his classic oil-drop experiment Weight Gravitational force (fg) Mass x Acceleration due to gravity (AG) (9.8 m/s2) Ex: 45 kgx 9.8 m/s2= 441 kg m/s2 N Force (F)= QE (charge of the particle)electrical Field Atomic Symbol Ion ZA X +1 Change proton, change element Ion- gain or lose Atom turns into an ion when electrons transfer to another element through chemical reaction When they combine with other elements to have a noble gas configuration Only stop reacting when it is stable like the Noble gasses + Cation - Anion Isotopes Same atomic number, different mass Measured using a mass spectrometer Difference in the number of neutrons, lessens the repulsion Relative Atomic Mass (Ar) Equals average mass of all the isotopic atoms present in the element Percentage Abundance- Percentage of each isotope of an element Formula- Percent1 x Mass1 + Percent2 x Mass2/ Total percentage Example= Bromine consists of 50% 79Br and 50% 81Br, calculate the Ar of Bromine Ar = [(50x79) + (50x81)]/100= 80 Relative Atomic mass of bromine is 80 or RAM or Ar (Br)= 80 Sub shell Found within the energy levels With increasing energy they are also called: s- Sharp p- Principal d- Diffuse f- Fundamental Orbitals Atomic Symbol Pb Se Cr F Nb X p+ no e- A +C 82 34 24 9 41 82 34 24 9 41 125 45 28 10 52 80 34 21 9 35 207 79 52 19 93 +2 0 +4 0 +6 Atomic Notation 82 207 Pb +2 34 79 Se 0 24 52 Cr +4 9 19 F 0 41 93 Nb +6 VI. Electron Arrangement VI. Rules governing electronic configuration Charge Mass Experiments Scientist -1.602x 9.109x Cathode Ray JJ Thomson 10-19 C 10-31 kg Oil Drop Robert Milikan Electron Mnemonic Device Sublevel Principle Quantum Numbers A three dimension area of space that surrounds the nucleus in which there is at least a 95% change of finding an electron with a known amount of energy Smaller spaces 7-f, 5-d, 3-p, 1-s S- sphere, p- dumbbell, d- clover, f- undefined 1 1s 2 2s 2p 3 3s 3p 3d 4 4s 4p 4d 4f 5 5s 5p 5d 5f 6 6s 6p 6d 6f 7 7s 7p 7d 7f Energy Levels Coined when atom was observed to emit e-rays at defined levels Given values from 1, 2, 3 X ray- Wilhelm Conrad Roentgen Photo electron Measurement Aufbau’s Principle states that energy levels must be filled from the lowest to highest and you may not move on the next level unless the previous level is full 5 electrons- 1s2 2s2 2p1 Calcium 20- 1s2 2s2 2p6 3s2 3p6 4s2 4s2 before d because it is shielded by the attractive force of the proton Noble Gases Chemical elements in group 18 of the periodical table The most stable due to having the maximum number of valence electrons their outer shell can hold Noble Gas Core Configuration Abbreviated way Shows just the electrons since the last noble gas Noble gas configuration Orbital Max. orbital Max. electron s 1 p 3 d 5 f 7 2 6 10 14 Energy Level # sublevel 1 2 3 4 2 3 4 4 # orbital Max. Electron 1 2 4 8 9 18 16 32 Hund’s Rule The most stable arrangement of electrons is that with the maximum number of unpaired electrons, all with the same spin direction (one electron goes in an orbital at a time before doubling up) Pauli’s Exclusion Principle No two electrons in an atom can have the same set of four quantum numbers (only 2 electrons can be in an orbital and they must have opposite spins) Shell Configuration Bohrs Model Valence Shell- Outermost or main energy shell Valence Electron- Electrons in the Valence Shell Inner core Electron- Electrons between the nucleus and valence electrons Box Configuration Orbital- spin- reduce the repulsive charge of the negatively charged electron Up- clockwise, down- counter clockwise Diamagnetic- all electrons are paired Paramagnetic- 1 or more electrons have no pair VII. Quantum Numbers Electrons Address Principal Quantum number Main energy level (n) 1, 2, 3, 4, 5, 6, 7 Azimuthal or Angular Momentum Quantum Number Sublevel (l) s- 0, p-1, d-2, f-3 Spin Quantum Number Direction Counterclockwise- ½ Clockwise- -1/2 Magnetic Quantum Number S- Spherical- 1 box, r: 0 P- dumbbell- 3 boxes, r: -1, 0, 1 D- Clover- 5 boxes, r: -2, -1, 0, 1, 2 F- unidentified- 7 boxes, r: -3, -2, -1, 0, 1, 2, 3 Examples n=1, l=0, ml=0, ms= +1/2: 1s1- H n= 4, l=3, ml=2, ms= +1/2: 4f6- Sm n= 6, l=1, ml=1, ms= -1/2: 6p6- Rh n= 4, l=2, ml=0, ms= +1/2: 4d3- Nb n= 2, l=0, ml=0, ms= -1/2: 2s2- Be
