INTRODUCTION TO GENERAL CHEMISTRY Basic Principles
INTRODUCTION TO GENERAL CHEMISTRY Basic Principles Scientific Method • A systematic approach to research • Hypothesis: a tentative explanation for a set of observations and experiments • Law: a description of a phenomenon that allows for general predictions • Theory: a well-established explanation for scientific data; not fully tested; can be disproven • Experiments: systematic observations and measurements performed under controlled conditions http://catalog.flatworldknowledge.com/bookhub/4309?e=averill_1.0-ch01_s02 What is Chemistry? • Chemistry is a scientific discipline that studies the inner properties of matter • Chemistry studies reactions between different substances and formation of new molecules http://marinebio.org/oceans/ocean-chemistry/ http://pchchemistry.weebly.com/why-study-chemistry.html What is matter? • Matter is any physically present substance that has a mass and occupies space • Matter is composed of atoms and molecules • Chemistry studies changes that occur in matter at the atomic and molecular level http://www.nasa.gov/mission_pages/themis/auroras/sun_earth_connect.html#.VCCNTaXN09c Classification of Matter Matter Pure matter Elements Compounds Mixtures Homogeneous Mixtures (solutions) Heterogeneous Mixtures Examples • Copper wire • A cup of tea • Oil / petroleum oil • Sea water • İron • Steel (alloy of iron and carbon) Units and Measurement • A measured quantity is given with a number and a unit • There are two common types of units used in science; metric units and SI units; SI units were derived from metric units but contain only one metric unit for each quantity Base quantity Name of unit symbol length meter m mass kilogram kg time second s temperature kelvin K Amount susbtance mole mol Prefixes Used with SI Units prefix symbol Meaning of the prefix giga G 109 mega M 106 (1000000) kilo k 103 (1000) deci d 10-1 (0.1) centi c 10-2 (0.01) milli m 10-3 (0.001) micro u 10-6 nano n 10-9 1 mL = 0.001 L 1 Mbytes = 1000000 bytes 1 nm = 0.000000001 m Common Measurements in Chemistry • Mass: measure of the amount of matter in a sample (kg, g) – mass is constant everywhere; (weight is not same as mass and it is the force that is applied on a object by gravity) • Volume: SI unit is m3, liter (L) is also used commonly; 1 L = 1 dm3 • Temperature: average kinetic energy of the atoms or molecules in a substance unit symbol Water freezes Water boils Celsius °C 0 100 Fahrenheit °F 32 212 Kelvin K 273 373 Common Measurements in Chemistry • Energy: capacity to perform a work, calorie (cal) and joule (J), 1 cal = 4.18 J • Density: mass per volume density = mass / volume “ g/mL “ is the unit commonly used substance Density (g/mL) air 0.001 ethanol 0.79 water 1.00 mercury 13.6 Sea water 1.02-1.03 (surface), up to 1.05 Oil (diesel) 0.832 Scientific Notation • In order to deal correctly with extremely large or extremely small numbers, we use scientific notation ( N × 10n, N is a number between 1 and 10) • Examples: 548.736 0.0000345 5.49 × 102 3.45 × 10-5 Significant Figures • What is significant figures? - Meaningful digits in a measured quantity • Often impossible to report the exact value of a quantity from a measurement – there is always some error • The margin of error (uncertainty) should be indicated clearly – this is done by indicating the number of significant figures • The last digit is meant to be uncertain – indicates the error margin Rules for determining significant figures: 1) All non-zero digits are significant (both before and after decimal point) 2) Zeros to the left of the first non-zero digit aren’t significant 3) If the number ends with zeros at the right of the decimal point, those zeros are significant - 4) If a number ends in zeros to the left of the decimal point, those zeros might be significant or not (writing in exponential form solves this uncertainty) - - - - - When we report a set of numbers, there should be consistency in the number of significant figures Calculations with significant figures • Addition and subtraction: When adding/subtracting numbers having different number of significant figures, the result must be reported with the same number of decimal places as the original number that has the fewest decimal places (rounding-off) • Multiplication and division: The result of multiplication or division can’t have more significant figures than the original number with fewest significant figures • Exact numbers (e.g. number of objects, unit definitions) are considered to have infinite number of significant figures Accuracy and Precision • Accuracy: how close is a measurement to the true value of the measured quantity • Precision: how close are two or more measurements of the same quantity match each other https://acontent.atutorspaces.com/home/course/content.php?_cid=783 Elements Name Symbol • An element is a single substance Aluminum Al in its simplest form that cannot be split into any more separate substances by chemical means • Everything around us is comprised of chemical elements • 112 elements, 90 of them naturally occurring • Only 2 elements are liquid at RT (bromine and mercury) and 11 are gases; all the rest are solids at RT Carbon C Copper Cu Iron Fe Oxygen O Potassium K http://science.jrank.org/kids/pages/212/Common-Elements.html Periodic Table • Periodic table is a chart in which elements with similar physical and chemical properties are grouped in a periodic way • The elements are arranged according to their atomic number • In a periodic table, horizontal rows are called periods and vertical groups are called groups • Elements within each group have similar chemical and physical properties • Groups 1-2 and 13-18 are called main group elements (also called 1A through 8A groups) • Groups 3-12 are called transition group elements (also called 3B through 12B group elements) Periods PeriodicTheTable Periodic Table of the Elements, in Pictures Alkali Metals Group 1 H Hydrogen Atomic Symbol 1 Symbols A _____ium Gas Examples at room temperature Z Name metallic solid red liquid colorless gas Human Body top ten elements by weight Earth's Crust top eight elements by weight Magnetic 4 3 Be Beryllium Lithium Li Liquid The color of the symbol is the color of the element in its most common pure form. ferromagnetic at room temperature Widgets 2 Noble Metals corrosion-resistant Radioactive Batteries Na Emeralds How it is (or was) used or where it occurs in nature all isotopes are radioactive Only Traces Found in Nature Metals Nonmetals Transition Metals Boron Group 13 B Boron Carbon Group 14 5C Carbon Nitrogen Group 15 6N Nitrogen 7O Oxygen Group 16 Oxygen Halogens 17 8F Fluorine Helium 2 1 Balloons 9 Ne Neon 10 Superheavy Elements 2 Rare Earth Metals Actinide Metals less than a millionth percent of earth's crust only made by people 3 He H Never Found in Nature 12 11 Mg Magnesium Sodium Noble Gases 18 Color Key Noble Gases Halogens als s et oid nm all r No Met Poo ls ta Me Sun and Stars Alkali Earth Metals 2 number of protons Solid Alkali Earth Metals Alkali Metals 1 Atomic Number Sports Advertising Basis of Life's Air Protein Toothpaste Equipment Signs Molecules 16 Cl 15 S 18 17 Ar 14 P Al 13 Si Sulfur Phosphorus Argon Chlorine Silicon Aluminum 3 Transition Metals Swimming Stone, Sand, Egg Yolks Bones Light Bulbs Chlorophyll Airplanes 3 4 5 6 7 8 9 10 11 12 Pools and Soil 30 Ga 29 Zn 28 Cu 27 Ni 25 Fe 26 Co 24 Mn 23 Cr 22 V 21 Ti 20 Sc 19 Ca 34 Br 33 Se 36 35 Kr 31 Ge 32 As Zinc Copper Nickel Cobalt Manganese Iron Chromium Vanadium Titanium Scandium Calcium Potassium Selenium Arsenic Krypton Bromine Gallium Germanium Salt K 4 4 Brass Electric Stainless Shells and Fruits and Photography Light-Emitting Semiconductor Steel Coins Magnets Earthmovers Structures Springs Aerospace Bicycles Copiers Poison Flashlights Instruments Diodes (LEDs) Electronics Wires Steel Bones Vegetables Film 48 In 47 Cd 46 Ag 45 Pd 44 Rh 43 Ru 42 Tc 41 Mo 40 Nb 39 Zr 38 Y Rb 37 Sr 51 Te 53 Xe 50 Sb 49 Sn 52 I 54 Cadmium Silver Palladium Rhodium Ruthenium Molybdenum Technetium Niobium Zirconium Yttrium Strontium Rubidium Antimony Iodine Tin Indium Tellurium Xenon 5 5 Global Navigation Cs Cesium Fireworks 55 Ba Barium 56 Pollution Searchlight Electric Radioactive Cutting Mag Lev Chemical Car Plated Liquid Crystal Thermoelectric High-Intensity Paint Jewelry Disinfectant Control Reflectors Switches Diagnosis Tools Trains Pipelines Batteries Displays (LCDs) Food Cans Coolers Lamps Hf 72 Ta 78 Au 79 Hg 86 77 Pt 85 Rn 76 Ir 84 At 75 Os 83 Po 74 Re 82 Bi 73 W 80 Tl 81 Pb Hafnium Platinum Gold Radon Iridium Astatine Osmium Polonium Rhenium Bismuth Tungsten Lead Tantalum Mercury Thallium Rare Earth Metals 6 X-Ray Atomic Diagnosis Clocks 88 Fr 87 Ra Radium Francium 89 - 103 Actinide Metals 7 8 Lasers 57 - 71 Laser Atom Traps 119 Luminous Watches 120 121 - 153 Rare Earth Metals Actinide Metals 6 Nuclear Mobile Surgical Anti-Static Radioactive Rocket Fire Lamp Low-Temperature Labware Jewelry Spark Plugs Pen Points Weights Thermometers Thermometers Submarines Phones Implants Medicine Brushes Engines Sprinklers Filaments Rf 104 Db 109 Ds 110 Rg 117 Uuo 118 107 Hs 108 Mt 115 Lv 116 Uus 105 Sg 106 Bh 113 Fl 114 Uup 111 Cn 112 Uut Meitnerium Darmstadtium Roentgenium Copernicium Bohrium Hassium Dubnium Seaborgium Ununtrium Flerovium Ununpentium Livermorium Ununseptium Ununoctium Rutherfordium Superheavy Elements 7 radioactive, never found in nature, no uses except atomic research 58 Pr La 57 Ce 65 Dy 64 Tb 71 70 Lu 63 Gd 67 Er 69 Yb 59 Nd 60 Pm 61 Sm 62 Eu 66 Ho 68 Tm Cerium Lanthanum Terbium Gadolinium Lutetium Ytterbium Europium Holmium Thulium Samarium Dysprosium Erbium Praseodymium Neodymium Promethium 6 Lighter Telescope Fluorescent Smart Material MRI Scientific Photodynamic Color Laser Laser Torchworkers' Electric Motor Luminous Electric Motor Optical Fiber Flints Lenses Lamps Diagnosis Medicine Fiber Lasers Dials Televisions Surgery Surgery Eyeglasses Magnets Magnets Actuators Communications Ac 89 Th 97 Cf 96 Bk 95 Cm 102 Lr 103 93 Pu 94 Am 98 Es 99 Fm 91 U 92 Np 100 Md 101 No 90 Pa Actinium Berkelium Curium Americium Nobelium Lawrencium Neptunium Plutonium Californium Einsteinium Protactinium Uranium Fermium Mendelevium Thorium 7 Classification of Elements 17 nonmetals 8 semimetals Elements metals Good conductors of electricity and heat Malleable Shiny All are solids at RT, except Hg Semimetals (metalloids) Intermediate properties between metals and nonmetals nonmetals Poor conductors of heat and electricity Are not shiny Might be gas, liquid and solid brittle Descriptive Names for Groups in the Periodic Table • 1A – alkali metals: lithium, sodium, potassium are most common, very reactive against air and water, hydrogen (H) is also in this group, but it is not a metal • 2A – alkaline earth metals: magnesium and calcium are the most abundant in nature among the group, found mainly as minerals • 7A – halogens: fluorine, chlorine, bromine, iodine are the most common – halogens react readily with metals to form salts (sodium chloride, calcium chloride) • 8A – noble gases: helium, neon, argon, krypton, xenon, radon – they are very unreactive gases – also called inert gases, they are present in monoatomic form • Transition metals (B group elements) – contain many of the common metals, such as iron, nickel, copper, cobalt, zinc, platinum, gold, silver Compounds • Compounds are pure substances that consist of two or more atoms of different elements held together by covalent or ionic bonds • The smallest structural unit of a compound is molecule • Compounds can be separated into smaller parts by chemical reactions • Compounds have a defined chemical structure (fixed ratio of atoms) – molecular formula • Examples; water (H2O) is a compound made of H2O molecules • Table salt (NaCl) is a compound made by NaCl units (ionic network) Changing of The Three States of the Matter • The extent of physical (non-covalent) interactions between molecules determines the physical state of a substance; solid, liquid, gas • Solid > liquid > gas (the order of the strength of non-covalent interactions) • The physical state of a substance can be changed by altering the number of non-covalent interactions between its molecules; this is achieved by giving or taking energy from the substance – generally by heat energy http://scienceehs.blogspot.com.tr/2011/09/three-states-of-water.html Three States of Matter • As we increase the energy of a substance, its molecules exhibit greater degree of movement and finally overcome the attractive forces holding the molecules together • Polar molecules have higher melting and boiling points, non-polar molecules have lower melting and boiling points (water b.p. =100 °C vs. methane b.p.= -161 °C) http://www.edplace.com/worksheet_preview.php?eId=2914&type=topic Atomic Theory • Theories of atom goes back to ancient Greek (Democritus) • First modern atomic theory is by John Dalton in 1808 • Summary of Dalton’s Atomic Theory: • 1) Elements are composed of very small particles, called atoms • 2) All atoms of an element are identical, but they are different than atoms of other elements • 3) Compounds (Bileşik) are composed of atoms of more than one element. The ratio of numbers of different atoms in a compound is an integer or simple fraction (law of definite proportions – sabit oranlar kanunu) • 4) A chemical reaction includes separation, combination or rearrangement of atoms, not their creation or destruction Atoms and Atomic Theory • The smallest unit (particle) of an element is atom • Atom is made up of subatomic particles; protons, neutrons and electrons – number of these determine the characteristic of an atom http://physics.taskermilward.org.uk/KS4/additional/html/atomic_structure.htm Atoms • Atomic Number (Z): number of protons (or electrons in a neutral atom) in an atom • Mass Number (A): (number of protons) + (number of neutrons) http://physicsnet.co.uk/gcse-physics/atomic-structure/ neutrons. In general, the mass number is given by mass number 5 number of protons 1 number of neutrons 5 atomic number 1 number of neutrons (2.1) The number of neutrons in an atom is equal to the difference between the mass number and the atomic number, or (A 2 Z). For example, if the mass number of a particular boron atom is 12 and the atomic number is 5 (indicating 5 protons in the nucleus), then the number of neutrons is 12 2 5 5 7. Note that all three quantities (atomic number, number of neutrons, and mass number) must be positive integers, or whole numbers. Atoms of a given element do not all have the same mass. Most elements have two or more isotopes, atoms that have the same atomic number but different mass numbers. For example, there are three isotopes of hydrogen. One, simply known as hydrogen, has one proton and no neutrons. The deuterium isotope contains one proton and one neutron, and tritium has one proton and two neutrons. The accepted way to denote the atomic number and mass number of an atom of an element (X) is as follows: mass number 8n atomic number 8n A ZX http://commons.wikimedia.org/wiki/File:Atomic_number_depiction.jpg Atoms and Ions • Ions: gain electron – anion, lose electron – cation (fluoride, F- ; sodium cation, Na+) • Atoms form ions as part of their reaction with other atoms to form molecules. • The readiness with which an atom gains or loses electrons dictates its reactivity 19 • F + 1e- 9 Neutral fluorine atom 9 protons, 9 electrons 19 F- 9 Fluorine anion 9 protons, 10 electrons Isotopes of Atoms • Isotopes: atoms with the same number of protons and electrons, but different number of neutrons 16O, 17O, and 18O • Elements are present in nature as mixtures of their isotopes • Chemical behaviors of isotopes are identical, nuclear properties might be different; radioactivity • Atomic mass of an element is the weighted average mass of all the isotopes – not same as mass number • 35Cl (~75.8%) and 37Cl (~24.2%) – atomic mass is 35.45 http://chemistry.tutorcircle.com/inorganic-chemistry/isotopes.html http://chemistry.tutorcircle.com/inorganic-chemistry/isotopes.html Representation of Atoms: Lewis Symbols • Representing atoms by showing only the valance electrons • Electrons (valance) are represented as dots around the chemical symbol of the atom • Dots can be placed on the 4 sides of the chemical symbol – place one electron each Each unpaired dot is available side, then start to add for bonding with other atoms remaining electrons https://classes.lt.unt.edu/Fall_2010/CECS_5030_026/mrp0113/Lewis%20Dot%20Project%20Page.h Atomic Orbitals and Energy Levels • Electrons of an atom are found in discrete shells around the nucleus – from closest to the nucleus to the farthest (valance shell) • These shells also correspond to energy levels; (n = 1, n = 2 etc.) • The energy level corresponds to the period number at the periodic table (hydrogen, n = 1, period 1) (Lithium, n = 2, period 2) Valance shell Calcium (Ca) is in the 4th period http://gcsechemistryhelp.tumblr.com/post/6753442513/periodic-table-electron-shells-part-1 Atomic Orbitals and Energy Levels • 1) Principal energy levels: Shown as n = 1, 2, 3 etc. – total electron capacity of a principal energy level is equal to 2(n)2 (for n=1, capacity 2 e-, for n=1, capacity 8 e-, for n = 3 capacity 18 e-) • 2) Sublevels: Within each principal energy level, there is a set of equal-energy orbitals – designated as s, p, d, f (Both principal energy level and type of sublevel is specified for describing the location of an electron) • 3) Orbital: Sublevels have atomic orbitals, which is a specific region of a sublevel where electron is located (probability of finding the electron is high); • 4) An orbital can have maximum 2 electrons Number of orbitals Electron capacity s 1 2 p 3 6 d 5 10 f 7 14 Octet Rule • Octet rule; atoms react in such a way that they have eight electrons in their valance (outermost) shell (more stable configuration) • This configuration of 8 electrons in the valance shell is also known as “noble gas configuration” • Noble gases (group 8A) are not reactive, since they have their valance shells already filled with 8 electrons (Helium is an exception and has 2 electrons in its only shell) • Other atoms lose/gain or share electrons to achieve the more stable noble gas configuration u By using octet rule, we can predict the chemical changes between atoms http://www.masterorganicchemistry.com/2010/08/14/from-gen-chem-to-org-chem-pt-7-lewis-structures/ Shapes of Orbitals 1 kind of s, 3 kind of p, 5 kind of d orbitals http://butane.chem.uiuc.edu/pshapley/GenChem2/Intro/2.html Electron configuration and Aufbau Principle • 1st principal energy level (n = 1) - 1s • 2nd principal energy level (n = 2) – 2s 2p • 3rd principal energy level (n = 3) – 3s 3p 3d • 4th principal energy level (n = 4) – 4s 4p 4d 4f • Aufbau principle: electrons fill the lowest-energy orbital that is available first How to write the electronic configuration of an atom? Rules: • 1) Start filling the orbitals from the lowest energy; (1s orbital is the lowest energy orbital) • 2) Each principle energy level contain n sublevels and each sublevel contain certain number of orbitals • 3) No more than 2 electrons can be placed in an orbital For example, 1s < 2s < 2p < 3s < 3p is the order of energy for the first three principal levels Be: 1s2 2s2 O: 1s2 2s2 2p4 Ne: 1s2 2s2 2p6 Mg: 1s2 2s2 2p6 3s2 http://www.amasci.net/knowledge/oxidation-states.php?lang=eng Molecular Interactions: How do molecules form? • Substances that are made of more than one element are called compounds, e.g. water (H2O) and carbon dioxide (CO2) • Valance electrons ; The valence shell holds the electrons located furthest from the nucleus • Valance electrons are important because; the rearrangement and redistribution of valence electrons between atoms enable atoms to ‘bond’ to one another • Full valance shell is the most stable form for an atom • The principal aim of chemical bond formation is to generate full valence shells Valance shell Chemical Bond Formation • There are two types of chemical bonding: 1) In a “covalent bond” one or more pairs of electrons are shared equally between the atoms 2) In an “ionic bond” electrons are totally transferred from one atom to another ü Two non-metal atoms will react to form a covalent compound ü A non-metal will react with a metal to form an ionic compound 1) Covalent Bond: Sharing of Electrons • In covalent bonding electrons are shared between atoms • The two orbitals with the valance electrons should overlap for covalent bond formation • This way the atoms sharing electrons gain full valance shell – more stable (octet rule) • Atoms which are linked by covalent bonds form discrete units called molecules; the smallest part of a single element (O2) or a compound (such as glucose, C6H12O6) • The molecular formula show the composition of one molecule of a covalent compound C 3H 8S (1-thiol), odour of onion C6H12O6 (glucose), sugar http://hyperphysics.phy-astr.gsu.edu/hbase/chemical/lewis.html 2) Ionic Bond: Transfer of Electrons • Ionic bonds are formed when one or more electrons are fully transferred from one atom to another – one atom becomes positively charged (cation) another becomes negatively charged (anion) • The attraction between the oppositely charged cations and anions makes the the ‘ionic bond’ between the ions - electrostatic interaction • Ionic compounds exist as extended lattices–a network of cations and anions • Ionic compunds have an overall charge of zero due to equal number of positive and negative charges within the compound http://www.chemguide.co.uk/atoms/structures/ionicstruct.html Covalent Bonds: Single and Multiple Bonds • Types of covalent bonds: Sigma (γ) and pi (π) bonds • Single or multiple bonds can form between two atoms • Single bonds are always sigma bonds • Single bond – one sigma bond • Double bond – one sigma bond + one pi bond • Triple bond – one sigma bond + 2 pi bonds http://hyperphysics.phy-astr.gsu.edu/hbase/chemical/lewis.html Polar Covalent Bonding and Electronegativity • Although there is no electron transfer in covalent bonding, the atoms making the covalent bond might have partial charges • In a heteroatomic molecule, the electron distribution around the molecule is not even; electrons are not shared equally – this gives partial charges to atoms • Electronegativity is the measure of the ability of an atom to attract electrons in a chemical bond • Electronegativity determines which of the atoms in a molecule will be partially negative and which will be partially positive http://apbrwww5.apsu.edu/thompsonj/Anatomy%20&%20Physiology http://bio1151b.nicerweb.net/Locked/media/ch02/ http://www.f.u-tokyo.ac.jp/~fukuyama/interactive_trial Chemical Bonding vs. Non-covalent (Intermolecular) Interactions • Non-covalent interactions are weak interactions between molecules • Non-covalent interactions determine physical properties such as boiling point, melting point, density etc. • These interactions are very important in biological systems (assembly of lipid bilayers, packing of genome etc.) • Although they are weak, multiple non-covalent interactions occur at the same time between two molecules to give a large overall effect Type of Interaction Energy Covalent 20-100 kcal/mole Van der Waals 1-2 kcal/mole Hydrogen bond 3-5 kcal/mole Dipole-dipole Ion-dipole
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