Chemistry 1210 Chapter 2 Notes
Chemistry 1210 Chapter 2 Notes Chem 1210
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This 13 page Class Notes was uploaded by Emily Notetaker on Tuesday September 6, 2016. The Class Notes belongs to Chem 1210 at Ohio State University taught by Dr. Bartoszek-Loza in Summer 2016. Since its upload, it has received 23 views.
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Date Created: 09/06/16
Sections 2.1 - 2.4 Overview Wednesday, August 24, 2016 10:35 AM Chapter 2 : Atoms, Molecules, and Ions 2.1 | The Atomic Theory of Matter • Early greek philosophers like Democritus believed that the material world was made up of tine indivisible particles called "atomos" • Later Plato and Aristotle stated that these particles were not possible • John Dalton eventually formulated the notion off atoms that he used to measure amounts of atoms when they reacted with other substances ○ Dalton's Atomic Theory 1. Each element is composed of extremely small particles called atoms. 2. All atoms of a given element are identical, but the atoms of one element are different from the atoms of all other elements. 3. Atoms of one element cannot be changed into atoms of a different element by chemical reactions; atoms are neither created nordestroyed in chemical reactions. 4. Compounds are formed when atoms of more than one element combine; a given compound always has the same relative number and kind of atoms. 2.2 | The Discoveryof Atomic Structure • The atoms is composed of subatomic particles : electrons, neutrons, and protons. ○ Cathode Rays and Electrons: Electrical discharge through a glass tube, pumped empty air . When a high voltage was applied to electrodes in tube, radiation was produced between electrodes. This radiation is called cathode rays - where they originated at the negative electrode and traveled to the positive electrode More experiments under J. J. Thomson showed that the cathode rays were deflected by magnetic or electric fields in a way that was consistent with a negative electrical charge. □ Described the cathode rays as streams of negatively charged particles. □ Led to the discovery of the electron. And then the charge - to - mass ratio 1.76 C/g □ ○ Oil Drop Experiment: Robert Milikan was able to measure the charge of an electron by allowing drops of oil to fall between electrically charged plates. Milikan changed the voltage between the plates, and measured how that affected the rate of the fall. He found the value of the charge to be 1.602 x C This allowed for the electron mass to be found from the value of the charge and Thomson's ratio □ * g ○ Radioactivity: Henri Becquerel discovered that uranium spontaneously emits high - energy radiation or is radioactive. Ernest Rutherford then found there were three types of radiation: □ Beta - attracted to positively positively charged plate - fast moving particles □ Gamma - high energy radiation and does not carry a charge (x-rays) □ Alpha - positive charge that are attracted to negative plate - fast moving particles Chapter 2 Page 1 ○ The Nuclear Model of the Atom: Plum pudding model □ Thomson said the atom consists of a uniform positive sphere of matter where the mass is evenly distributed and the electrons are embedded like seeds. Nuclear Model: □ Rutherford observed in an experiment at which angles alpha particles were being deflected as they passed through gold foil. Almost all of the particles passed through, but went on to observe scattering at large angles which disproved the plum pudding model. The alpha particles were being deflected by a positive center (the nucleus). □ The model explained most of the mass of each atom and its positive charge reside in a small, dense region called the nucleus. And that most of the atom was empty space with electrons. □ Protons were discovered by Rutherford and neutrons were discovered by James Chadwick. 2.3 | The Modern View of the Atomic Structure • In modern times, the charge of the electron is expressed as -1 and a proton is expressed by +1. Neutrons are electrically neutral. • *Every atoms has an equal number of electrons and protons* • Protons and neutrons are in the nucleus of the atom. • Electrons are attracted to the protons in the nucleus by an electrostatic force. • Atomic Numbers: ○ The number of protons in an atom. ○ *The atoms of each element have a characteristic # of protons* • Mass number: ○ The amount of neutrons plus the protons. ○ Atoms can differ in the amount of neutrons and consequently in mass too. • Isotopes: ○ Atoms with identical atomic # but different mass #, because of different # of neutrons in nucleus. 2.4 | Atomic Weights • Measured in atomic mass units (amu) • Elements mostly occur as mixtures of isotopes so we can determine the average atomic mass or atomic weight of each element. Chapter 2 Page 2 Lecture #2 Thursday, August 25, 2016 2:22 PM Atomic Theory of Matter (2.1) • 400 BC: Matter consisted of very small indivisible particles, atomos. • 1800s(Dalton's hypothesis) - 2000 year gap ○ Law of multiple proportions: CO, CO 2 Mass of A that combines with the mass of B is a ratio of small whole numbers. AB, A B, AB 2 2 ○ Law of constant composition:H O 2 Proust (1799) - took different samples of the same substance contain the same proportion of atoms □ Water is always 11% H, and 88% O ○ Law of conservationof mass: Lavosier(1785) - During a chemical reaction, the total mass before the reaction is equal to the total mass after the reaction Discoveryof Atomic Structure (2.2) 1850s:atoms composedof charged particles • Thompson:charge to mass ratio (C/g) • Milikin: charge of an electron e mass = 9.10 *10 -28g • Rutherford : alpha, beta, and gamma rays • The Nuclear Model of the Atom ○ Thompson:plum pudding ○ Rutherford: electron scattering ○ Chadwick: neutron Atomic Structure - Modern View (2.3) • Can see spider web thread: 0.0001cm -10 -14 • Atom: 10 m Nucleus: 10 m • Isotopes: Same atomoicnumber (p, e-), different mass (neutrons) ○ Hydgrogen: H, H (deuterium), H (tritium) 235 238 ○ Uranium: U, U • Mass spectrometer:device to determineatom mass --- make ions --- pass between magnetic poles -- speed depends on mass Quiz 2 Tuesday, August 30, 2016 2:29 PM -Know all of the Anions and Cations for the Quiz Consider the following formulas: SO2, CH, C4H2O2. Which of these could be only molecular formulas? Lecture #3 Tuesday, August 30, 2016 2:42 PM Atomic mass/weight (2.4) • 1st: 100.0g of water: 11.1 g H, 88.9 g O ○ 8x as much O as H • 2nd: Water contained 2 H for each O ○ Found 2 H/water - 16x as much O as H • H arbitrarily assigned relative mass of 1 • Atomic masses of all other atoms were assigned relative to H, i.e. O = 16 Today masses of individual atoms are determined with a high degree of accuracy: • 1H atom: 1.6735 x 10 -24g 16 -23 • O atoms: 2.6560 x 10 g By definition: 1 amu = 1.66054 x 10 -24g and 1 g = 6.02214 x 10 amu 12 • Amu precisely defined by assigning a mass of exactly 12 to C ○ H 1.0078 amu 16 ○ O is 15.9949 • Average Atomic Mass: isotopes/abundance 98.93% C and 1.07% C gives C=12.01 ○ Also known as the atomic weight The Periodic Table (2.5) • Vertical columns: A, B groups (~ ox #) • Horizontal rows: periods (e configuration: s, p, d) • Metals: left side ○ 1A (alkali, +1), 2A(alkali earth, +2) • Nonmetals: top right side ○ 7A (halogens, -1), 8A(noble gases) • Metalloids: steps … B, Si, Ge, As, Sb, Te, Po, At Properties • Metals: conducts electricity and heat, malleable, ductile, luster, all (s) except Hg, form cations, form ionic compounds • Nonmetals: does NOT conduct, variety of color, appearance, gases or brittle solids (except Br ), i2sulators form anions, molecular compounds • Metalloids: in between … metallic and nonmetallic properties Molecules, Molecular Compounds (2.6) Molecule: combination of at least two atoms in a specific arrangement held together by chemical forces (atoms share electrons). Always contains a nonmetal • Diatomic: molecule made up of two identical atoms. H , N ,2O ,2F 2 Cl2Br 2,I 2 2 • Diatomic: molecule made up of two identical atoms. H , N , O ,2F ,2Cl 2r 2 I 2, 2 2 Chemical formula denotes the composition. • Empirical formula: simplest ratio of the atoms in a molecule. • Molecular formula ○ CH: C H2, 2 H 6 6 ○ CH : 22H , 4 H 3 C6H 4 8 • Allotropes: different forms of elements which have different chemical formulas. ○ Oxygen (O ) -2pertinent for humans and ozone(O ) - bad 3or humans Picturing molecules (on slide everything represents methane) • Structural formula - arrangement (2D) • Molecular geometry - 3D (VSEPR) • Space filling models • Computer simulations Ions and Ionic Compounds (2.7) Ion: atom (or group of atoms) that has a net positive or negative charge. • Cation: loss of electron(s)-- will become less negative ○ metals • Anion: gain electron(s) -- will become more negative ○ nonmetals ○ Chlorine then to Chlor(eye)n The name changes when the amount of electrons change **Metals form cations, Nonmetals form anions** Polyatomic ions: two or more atoms 2- 3- + • NO -,3CO , P3 , NH4 4 Ionic compounds: electron transfer occurs. Consists of cations and anions • NaCl, Na(NO ) , 3 2OH 4 • Common Ions … Where are they on the periodic table? What are their charges Chapter 2 Page 7 • Cation(metal) and Anion (nonmetal) make an ionic bond Written formula examples: 2+ 2- Ca + CO 3 ----> CaCO 3 2NH +4S ---> (NH ) S 4 2 2Al + 3SO 42----> Al2(SO 4 3 Determine the charges on the atoms: CsF: +1 -1 = 0 Al2O 3 +3(2) - 2(3) = 0 Mg N : +2(3) - 3(2) = 0 3 2 Ca 3PO )4 2+2(3) - 3(2) = 0 **Know the following Cations** **Know the following anions** Naming Inorganic Compounds (2.8) Names/Formulasof Ionic Compounds Chapter 2 Page 8 Names/Formulasof Ionic Compounds • Write the cation, then the anion ZnCl 2 Potassium sulfide ○ Mg N Calcium oxide 3 2 • Cation name using name of element • Anions often use stem name for the element and the suffix -ide ○ Mono: H-, O2-, N3- ○ Poly: OH-, CN-, O22- • Metals having more than one possible charge, put cation charge in parenthesis: FeO Iron(II) Oxide Fe 2 3 Iron (III) Oxide CuCl Copper (I) Chloride ○ CuCl 2 Copper (II) Chloride SnCl 2 Tin (II) Chloride SnCl Tin (IV) Chloride 4 Cations: two common … NH +, H O+ 4 3 Polyatomic anion naming is systematic: • Oxygen containing anions (oxyanions): the naming system is based on - ate: 2- CO 3 Carbonate - NO 3 Nitrate 3- ○ PO 4 Phosphate SO 42- Sulfate ClO 3- Chlorate • Ion with one more oxygen atom has a prefix of per-: - ○ ClO -4- perchlorate • Ion with one less oxygen atom has ending of -ite: ClO 2- Chlorite NO - Nitrite ○ 2 - SO 3 Sulfite ○ One less oxygen then these atoms will have the prefix of hypo: ClO --- hypochlorite + • Addition of H to a 2- or 3- ion named by either adding bi- or hydrogen to name either adding bi- or hydrogen to name ○ CO /3CO 3- --- Bichlorate Names and Formulas of Acids • These compounds are not "ionic" but produce H+ in aqueous solution ○ HCl(aq) ---> H (aq) + OH (aq) • Strong acids: ○ HCl, HBr, HI, HNO , 3 SO2, 4ClO , H3lO 4 • Weak acids: any acid that is not strong ○ H S2 HNO , 2 SO2, H3lO, HClO 2 Names/Formulas of Binary Molecular Compounds Two nonmetals OR metalloid and nonmetal • Often cannot predict the name as with the ionics. • Element given first in the formula and named first is determine according to the following sequence Chapter 2 Page 9 Sections 2.5 - 2.9 Overview Thursday, September 1, 2016 8:42 AM Book Overview(pg. 52-71) 2.5 | The Periodic Table The periodic table was developed in 1869as many other elementswere being discovered. • Periods - horizontal rows • Groups - vertical columns ○ Elements in a group often exhibit similarities in physical and chemical properties Ex: Copper, Silver, and gold are less reactive than most metals • Metallic Elements or Metals - on the left and middle of periodic table ○ Characteristic Properties: Luster High electrical conductivity High heat conductivity All except mercury are solid at room temp. • Nonmetals - separate from metals with a stepped line on the right side ○ Some are solid at room temp, someare gaseous, and one is liquid ○ Differ in appearance from metals ○ Metalloids - elementsthat lie along the stair step line that have properties of both metals and nonmetals 2.6 | Molecules and Molecular Compounds **Only noble gases are found in nature as isolated atoms** • Chemicals Formula - represents a molecule ○ Ex: O 2 H2O • DiatomicMolecule - a molecule made up of two of the same atoms • DiatomicMolecule - a molecule made up of two of the same atoms ○ Ex: F 2 Cl2 ○ Elements that normally occur as diatomic molecules: Hydrogen, oxygen, nitrogen, flourine, chlorine, bromine, and Iodine □ They make a 7 on the periodic table so rememberthat there are 7 elements including oxygen • Molecular compounds - compoundscomposed of moleculesthat contain more than one type of atom ○ **Composedonly of nonmetallic elements** • Molecular formulas - chemical formulas that indicate the actual numbers of atoms in a molecule • Empirical formulas - give only the relative number of atoms in each molecule ○ The subscripts are always the smallest whole-number ratios Ex: hydrogen peroxide □ Molecular formula: H O 2 2 □ Empirical formula:HO ○ We can determine the empirical formula from the molecularformula but not vice versa • Structural formula - shows which atoms are attached to which, does not depict actual geometry ○ Geometry is shown by: Perspectivedrawing - portrays the three-dimensional shape of the structural formula Ball-and-stick models - show atoms as spheres and bonds as sticks Space-filling model - shows what a moleculewould look like if the atoms were to scale 2.7 | Ions and Ionic Compounds An atom's nucleus will never change, however,the electrons of an atomscan be gained or lost. • Ion - a charged particle that is a result from a removedor gained electron ○ Cation - a positively charged ion Always rememberthe difference because cation has a "t" which looks like a "+" ○ Anion - a negativelycharged ion Ex: If an atom has 11 protons and 11 electrons and loses one of its electrons,the result is a cation with a +1 charge 2- • Polyatomicions - atoms joined as a molecule,but carrying a net positive or negative charge (SO ) 4 Nobel gases rarely lose or gain electrons since they are chemically non-reactiveelements. Other groups on the periodic table gain or lose electrons in order to end up with the same number of electronsas the nobel gases. • Ionic compound - a compound made up of cations and anions ○ We can tell the difference between ionic and molecular compounds because ionic is generally combinationsof metals and nonmetals while molecular is only nonmetals ○ When writing empirical formulas you will see that if the charges are equal the subscript for the cation and anion will be 1, if the charges are not equal the charge of one ion will become the subscript for the other 2.8 | Naming Inorganic Compounds Chemical Nomenclature - the system used in naming substances, split into three divisions: • Ionic compounds: ○ Cations Cations formed from metal atoms have the same name as the metal Na + Sodium Ion 2+ Zn Zinc ion Al3+ Aluminum ion If a metal can form cations with different charges, the positive charge is indicated by a Roman numeral in parentheses following the name of the metal □ Most metals that form cations with different charges are transition metals(elementsin the middle of the periodic table) 2+ Fe Iron (II) ion Cu + Copper(I) ion Fe3+ Iron (III) ion 3+ Fe Iron (III) ion 2+ Cu Copper(II) ion Cations formed from nonmetal atomshave names that end in -ium NH + Ammonium ion 4 H3O + Hydronium ion ○ Anions The names of the monatomicanions are formed by replacing the ending of the name of the element with -ide, as well as a few polyatomicanions follow this rule H- Hydride ion 2- O Oxide ion 3- N Nitride ion - OH Hydroxide ion - CN Cyanide ion 2- O2 Peroxideion Oxyanions - Polyatomicanions containing oxygen that have names ending in -ate or - ite. The -ate is used for the most common/representativeoxyanion of an element, and -ite is used for an oxyanion that has the same charge but one O atom fewer. NO 3- Nitrate ion SO 42- Sulfate ion NO 2- Nitrite ion SO 32- Sulfite ion □ Prefixes are used for a series of oxyanions (per- is one more O atom than the oxyanion ending in -ate, hypo- is one less than the oxyanion ending in -ite) Anions derived by adding H to an oxyanion are named by adding as a prefix the word hydrogen or dihydrogen
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