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9/13/2015 CHAPTER 2 ATOMS, MOLECULES, AND IONS Prof. Dr. Nizam M. El-Ashgar THE ATOMIC THEORY OF MATTER Historically: Greek Philosophers: matter can be subdivided into fundamental particles. Democritus (460–370 BC) and other early Greek philosophers described the material world as made up of tiny indivisible particles they called atomos, meaning “indivisible or uncuttable.” The “atomic” view of matter faded for many centuries. The notion of atoms reemerged in Europe during the seventeenth century. That theory came from the work of John Dalton during the period from 1803 to 1807. ١ 9/13/2015 THE ATOMIC THEORY John Dalton’s 4 Postulates: 1. Each element is composed of extremely small particles called atoms. 2. All atoms of an element are identical to each other, but different than atoms of other elements. 3. Atoms of one element cannot be changed into atoms of different elements by chemical reactions; atoms are neither created or destroyed in reactions. 4. Compounds are formed when atoms of different elements combine in a definite ratio. I) LAW OF CONSERVATION OF MASS Mass is neither created nor destroyed in chemical reactions. 3.25 g + 3.32 g = 6.57 g Hg(NO3)2(aq) + 2KI(aq) HgI2(s) + 2KNO3(aq) 4.55 g + 2.02 g = 6.57 g ٢ 9/13/2015 II) THE LAW OF DEFINITE PROPORTIONS Different samples of a pure chemical substance always contain the same elements with constant proportion of elements by mass. By mass, water (H2O) is: 88.8 % oxygen 11.2 % hydrogen III) LAW OF MULTIPLE PROPORTIONS: If 2 elements combine to form more than one compound, and if one element presents in fixed mass the masses of the second element exist in small whole number ratios. Sample 1 H O 1 g 16 g Sample 2 H O 1g 8g H2O H2O2 mall whole number ratios: 2/1, 1/2, 3/2, 2/3, 3/4,,,,,,,, This follows from the postulate that individual atoms enter into chemical combination. ٣ 9/13/2015 THE DISCOVERY OF ATOMIC STRUCTURE J. J. Thomson (1898—1903) Postulated the existence of electrons using cathode-ray tubes. Determined the charge-to-mass ratio of an electron. The atom must also contain positive particles that balance exactly the negative charge carried by particles that we now call electrons. 7 Thomson’s Experiment Voltage source - + Cathode rays = radiation produced when high voltage is applied across the tube. The voltage causes negative particles to move from the negative electrode (cathode) to the positive electrode (anode). ٤ 9/13/2015 If no Magnetic and Electric field applied: The cathode rays pass in straight direction> Applying EF: The path of the cathode rays altered toward the +ve plate. Applying MF: The cathode rays can be deflected in opposite direction. By balancing both MF and EF: The rays pass in straight direction. Deflection of electron depends on three factors: 1) Strength of electric or magnetic field. 2) Size of negative charge. 3)Mass of the electron. In 1897 Thomson determined the charge-to-mass ratio of an electron. Charge/Mass = 1.76 108 C/g. C is a symbol for coulomb (SI of electric charge). Either the charge or the mass of an electron would yield the other. ٥ 9/13/2015 Oil Drop Experiment (Millikan, 1868–1953): Applied a voltage to oppose the downward fall of charged drops and suspend them. Voltage on plates place 1.602176 x 10-19 C of charge on each oil drop = electron charge. − 19 - 28 1.60× 10 C electronmass = = 9.10× 10 g 8 1.76× 10 C / g RADIOACTIVITY Radioactivity is the spontaneous emission by an atom. It was first observed by Henri Becquerel. Marie and Pierre Curie also studied it. Method: A radioactive substance is placed in a containing a small hole so that a beam of emitted from the shield. The radiation is passed between two charged plates and detected. ٦ of radiation lead shield radiation is electrically 9/13/2015 Three types of radiation were discovered by Ernest Rutherford: α particles: helium nucleus (+2 charge, large mass) β particles: high speed electron (-ve) γ rays: high energy light, similar to X-rays (no charge). The mass of an α -particle is 7300 times that of the electron (similar to X-rays) THE ATOM, CIRCA 1900 Early model: the “plum pudding” model. Thompson: proposed a positive sphere of matter with negative electrons imbedded in it. ٧ 9/13/2015 RUTHERFORD’S EXPERIMENT Used uranium to produce alpha particles Aimed alpha particles at gold foil by drilling hole in lead block 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 + ٨ 9/13/2015 Explanation: Atom is mostly empty. Small dense, positive piece at center in the nucleus. Alpha particles are deflected by it if they get close enough. Proton (p) has opposite (+) charge of electron (-) Mass of p is 1840 times the mass of e- (1.67 x 10-24 g). Protons were discovered by Rutherford in 1919. Neutrons were discovered by James Chadwick in 1932. + SUBATOMIC PARTICLES Protons and electrons are the only particles that have a charge. Protons and neutrons have essentially the same mass. The mass of an electron is so small we ignore it. ٩ Particle Mass (g) Electron (e-) 9.1 x 10-28 Proton (p+) 1.67 x 10-24 Neutron (n) 1.67 x 10-24 Mass (amu) Charge (Coulombs) Charge (units) 5.486 x 10-4 -1.6 x 10-19 -1 1.0073 +1.6 x 10-19 +1 1.0087 0 0 9/13/2015 The angstrom is a convenient non-SI unit of length used to denote atomic dimensions. 1 Å = 10 x 10 –10 m Density of nucleus: 1013–1014 g/cm3 A matchbox full of material of such density would weigh over 2.5 billion tons! SAMPLE EXERCISE 2.1 The diameter of a US dime is 17.9 mm, and the diameter of a silver atom is 2.88 Å . How many silver atoms could be arranged side by side across the diameter of a dime? Conversion Factors: 1 Å ↔ 10 -10 m ١٠ 1 Ag atom ↔ 2.88 Å 9/13/2015 PRACTICE EXERCISE The diameter of a carbon atom is 1.54 Å. (a) Express this diameter in picometers. (b) How many carbon atoms could be aligned side by side in a straight line across the width of a pencil line that is 0.20 mm wide? Answer: (a) 154 pm, (b) 1.3 ×106C atoms ATOMIC NUMBERS, MASS NUMBERS AND ISOTOPES Atomic Number (Z): Number of protons in an atom’s nucleus. Equivalent to the number of electrons around an atom’s nucleus Mass Number (A): The sum of the number of protons and the number of neutrons in an atom’s nucleus Isotope: Atoms with identical atomic numbers but different mass numbers ١١ 9/13/2015 All atoms of the same element have the same number of protons: The atomic number (Z) ISOTOPES Isotopes are atoms of the same element with different masses. Isotopes have different numbers of neutrons. ١٢ 11 6C 12 6C 13 6C C−11 C − 12 C − 13 14 6C C − 14 9/13/2015 ISOTOPES carbon-12 mass number 12 C 6 6 protons 6 electrons 6 neutrons 14 6 protons 6 electrons 8 neutrons atomic number carbon-14 mass number 6 atomic number C SAMPLE EXERCISE 2.2 How many protons, neutrons, and electrons are in (a) an atom of 197Au: From PT: Z = 79 P= 79 e = 79 n = 197-79 =118 (b) an atom of strontium-90? From PT: Z = 38 P= 38 e = 38 n = 90-38 = 52 ١٣ 9/13/2015 PRACTICE EXERCISE: How many protons, neutrons, and electrons are in (a) a 138Ba atom, (b) an atom of phosphorus-31? Answer: (a) 56 protons, 56 electrons, and 82 neutrons; (b) 15 protons, 15 electrons, and 16 neutrons. ATOMIC WEIGHTS: The Atomic Mass Scale : Early: It was related to H mass. Consider 100 g of water: • Upon decomposition 11.1 g of hydrogen and 88.9 g of oxygen are produced. • The mass ratio of O to H in water is 88.9/11.1 = 8. • Therefore, the mass of O is 2 x 8 = 16 times the mass of H. • If H has a mass of 1, then O has a relative mass of 16. We can measure atomic masses using a mass spectrometer. 1H mass = 1.6735 x 10–24 g 16O mass = 2.6560 x10–23 g. ١٤ 9/13/2015 Atomic mass units (amu): are convenient units to use when dealing with extremely small masses of individual atoms. The amu is 1/12 the mass of one 12C atom. 1 amu = 1.66054 x 10–24 g 1g = 6.02214 x1023 amu By definition, the mass of 12C is exactly 12 amu. Now all the present atoms are assigned according to C12 isotopes A 24Mg atom has a mass approximately twice that of the 12C atom, so its mass is 24 u. A 4He atom has a mass approximately 1/3 that of the 12C atom, so its mass is 4 u. 1H atom has a mass of 1.0078 amu. 16O atom has a mass of 15.9949 amu. MASS SPECTROPHOTOMETER Atomic and molecular masses can be measured with great accuracy with a mass spectrometer. ١٥ 9/13/2015 ATOMIC WEIGHT Most elements occur in nature as mixtures of isotopes. We can determine the average atomic mass of an element, usually called the element’s atomic weight. We average the masses of isotopes to give average atomic masses. Example: Naturally occurring C consists of: 12 6 C 13 6 C Atomic mass: 12.0 amu 13.00335 amu Abundance: 98.93 % 1.07 % • The average mass of C is: (0.9893)(12 amu) + (0.0107)(13.00335 amu) = 12.01 amu. Atomic weights are listed on the periodic table Because in the real world we use large amounts of atoms and molecules, we use average masses in calculations. ١٦ 9/13/2015 HW: Chlorine has two naturally occurring isotopes: Cl35 with an isotopic mass of 34.969 amu, and Cl-37 with an isotopic mass of 36.966 amu. The atomic weight of chlorine is 35.5 . What is the relative abundances of the two isotopes? 37 17 Cl 35 17 Cl Atomic mass Abundance: 34.969 amu X 36.966 amu 100-X ELEMENTS IN PERIODIC TABLES ١٧ 9/13/2015 SAMPLE EXERCISE 2.3 Magnesium has three isotopes, with mass numbers 24, 25, and 26. Write the complete chemical symbol (superscript and subscript) for each of them. 24 Mg 12 25 Mg 12 26 12 Mg (b) How many neutrons are in an atom of each isotope? The numbers of neutrons in an atom of each isotope are therefore 12, 13, and 14, respectively. PRACTICE EXERCISE Give the complete chemical symbol for the atom that contains 82 protons, 82 electrons, and 126 neutrons. ١٨ 9/13/2015 PRACTICE EXERCISE Three isotopes of silicon occur in nature: 28Si (92.23%), which has an atomic mass of 27.97693 amu; 29Si (4.68%), which has an atomic mass of 28.97649 amu; and 30Si (3.09%), which has an atomic mass of 29.97377 amu. Calculate the atomic weight of silicon. Answer: 28.09 amu PERIODIC TABLE It is a systematic catalog of the elements. Elements are arranged in order of atomic number. ١٩ 9/13/2015 Periods: The rows on the periodic chart. Columns: The groups on the periodic chart. Elements in the same group have similar chemical properties. Periods (Raws) Groups (columns) GENERAL ARRANGEMENT Metallic elements, or metals: Are located on the left-hand side of the periodic table (most of the elements are metals). Metals tend to be: malleable, ductile, and lustrous and are good thermal and electrical conductors. Nonmetallic elements, or nonmetals: Are located in the top right-hand side of the periodic table. Nonmetals tend to be brittle as solids, dull in appearance, and do not conduct heat or electricity well. Metalloids: Are located at the interface between the metals and nonmetals. Elements with properties similar to both metals and nonmetals These include the elements B, Si, Ge, As, Sb and Te ٢٠ 9/13/2015 NAMES OF SOME GROUPS IN THE PERIODIC TABLE These five groups are known by their names. IMPORTANT FAMILIES OF ELEMENTS Representative Elements: The elements in the A groups (1,2, 13-18). Transition Metals: The elements in B groups (3-12). Inner Transition Metals: The two rows of metals (lanthanides and actinides) set at the bottom of the periodic table. ٢١ 9/13/2015 SAMPLE EXERCISE 2.5 Which two of the following elements would you expect to show the greatest similarity in chemical and physical properties: B, Ca, F, He, Mg, P? Solution: Ca and Mg should be most alike because they are in the same group (2A, the alkaline earth metals). PRACTICE EXERCISE Locate Na (sodium) and Br (bromine) on the periodic table. Give the atomic number of each, and label each a metal, metalloid, or nonmetal. ٢٢ 9/13/2015 2.6 MOLECULES AND MOLECULAR COMPOUNDS Only Nobel gases are found in nature as isolated atoms. Most matter is composed of molecules or ions. A molecule: consists of two or more atoms bound tightly together. Types: 1) Molecular Elements: Same two or more atoms combined with each others. Diatomic molecules: made up of two same kind of atoms. Examples: N2, O2, Cl2 Polyatomic molecules: made up of more than two atoms of same atoms. Examples: S8, P4, O3 Allotropes: Different forms of an element, which have different chemical formulas Allotropes differ in their chemical and physical properties. Examples: Ozone (O3) and “normal” Oxygen (O2) C (diamond) and C (Graphite) 2) Molecular compounds: Composed of molecules which contain more than one type of nonmetallic atoms. Examples: - Diatomic: HCl, CO. - Polyatomic: H2SO4, HCl, CO2, H2O2, NH3 Molecules H2 ٢٣ H2O NH3 CH4 9/13/2015 CHEMICAL FORMULA Each molecule has a chemical formula. The chemical formula indicates : 1. which atoms are found in the molecule. 2. what proportion they are found. Types: 1) Molecular formulas (MF): These formulas give the actual numbers and types of atoms in a molecule. Examples: H2O, CO2, CO, CH4, H2O2, O2, O3, and C2H4. 2) Empirical formulas (EF): These formulas give the relative (simplest whole numbers ratio) numbers and types of atoms in a molecule Examples: H2O, CO2, CO, CH4, HO, CH2. MF = n (EF) Example: C2H6 = 2 (CH3) 3) Structural Formulas (SF): Structural formulas show the order in which atoms are bonded. Examples: Methane Ethane H ٢٤ H H C C H H H 9/13/2015 Different types of formulae of some compounds Compound Empirical formula Molecular formula Structural formula Carbon dioxide Water CO2 CO2 O = C =O H2O H2O Methane CH4 CH4 Glucose CH2O C6H12O6 O H H H H C H H OH O H H H OH H H OH HO Sodium fluoride NaF Not applicable OH Na+F- PICTURING MOLECULES Molecules occupy three-dimensional space. However, we often represent them in two dimensions by SF which usually does not depict the actual geometry of the molecule, that is, the actual angles at which atoms are joined together. Perspective drawings: use dashed lines and wedges to represent bonds receding and emerging from the plane of the paper. Molecular Modeling: Ball-and-stick models : show atoms as contracted spheres and the bonds as sticks. • The angles in the ball-and-stick model are accurate. Space-filling models: give an accurate representation of the 3-D shape of the molecule. ٢٥ 9/13/2015 ٢٦ 9/13/2015 SAMPLE EXERCISE 2.6 Write the empirical formulas for the following molecules: (a) glucose, whose molecular formula is C6H12O6. Solution: Divide by 6 so EF is CH2O. (b) nitrous oxide, a substance used as an anesthetic and commonly called laughing gas, whose molecular formula is N2O. Solution: EF is N2O Practice Exercise: Give the empirical formula for the substance called diborane, whose molecular formula is B2H6. Answer: BH3 IONS AND IONIC COMPOUNDS Ions: Species pear charge (-ve or +ve) and formed by adding or removing electrons. • Cations: Formed when an atom or molecule loses electrons and becomes positively charged. Metals tend to form Cations by losing electrons. Anions: Formed when an atom or molecule gains electrons and becomes negatively charged. Nonmetals tend to form Anions by gaining electrons. Generally atoms gain or lose electrons to attain the noble gas elements (stable uncreative elements). ٢٧ 9/13/2015 MONOATOMIC IONS Anions or Cations of only one atom. Cations of Representative elements have a (+ve) charge = group number. (GI A =1+, G2A=2+, Al=3+) Cations formed from metal atoms have the same name as the metal: Na+ sodium ion Zn2+ 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: Cation Cu+ Cu2+ Stock Name Old Name copper(I) ion Cuprous ion copper(II) ion Cupric ion Cation Fe2+ Fe3+ Stock Name Iron(II) ion Iron(III) ion Old Name Ferrous ion Ferric ion Cations formed from nonmetal atoms have names that end in -ium: NH4+ ammonium ion H3O+ hydronium ion Anions of Representative elements have a (–ve) charge = 8- group number. The names of monatomic anions are formed by replacing the ending of the name of the element with -ide: H- hydride ion O2- oxide ion N3- nitride ion A few polyatomic anions also have names ending in -ide: OH- hydroxide ion CN- cyanide ion ٢٨ O2- peroxide ion 9/13/2015 PREDICTING THE CHARGE OF IONS Cations: are positive and are formed by elements on the left side of the periodic chart. Anions: are negative and are formed by elements on the right side of the periodic chart. POLYATOMIC IONS When molecules lose electrons, polyatomic ions are formed: ٢٩ NH4+ ammonium SO42- sulfate CO32- carbonate SO32- sulfite HCO3- bicarbonate NO3- nitrate ClO3- chlorate NO2- nitrite Cr2O72- dichromate SCN- thiocyanate CrO42- chromate OH- hydroxide 9/13/2015 SAMPLE EXERCISE 2.7 Give the chemical symbol, including mass number, for each of the following ions: (a) The ion with 22 protons, 26 neutrons, and 19 electrons. 48 3+ 22 Ti (b) The ion of sulfur that has 16 neutrons and 18 electrons. 32 16 S2- Practice Exercise: How many protons, neutrons, and electrons does the 79Se2– ion possess? Answer: 34 protons, 45 neutrons, and 36 electrons SAMPLE EXERCISE 2.8 Predict the charge expected for the most stable ion of barium and for the most stable ion of oxygen. Solution: Ba → 2+ Symbol: Ba2+cation. O → 2Symbol: O2-cation. Practice Exercise: Predict the charge expected for the most stable ion of : (a) aluminum and (b) fluorine. Answer: (a) 3+; (b) 1– ٣٠ 9/13/2015 IONIC COMPOUNDS An ionic compound is composed of cations and anions joined to form a neutral species. Ionic compounds generally form from the combination of metals with nonmetals. In ionic compounds each cation is surrounded by several anions and vice versa. Crystal WRITING FORMULAS OF IONIC COMPOUNDS The formula of an ionic compound is an empirical formula that uses the smallest whole number subscripts to express the relative numbers of ions. The relative numbers of ions in the empirical formula balances the charges to zero. Example: If these subscripts are not in the lowest whole-number ratio, divide them by the greatest common factor. Al 3+ + PO43- = Al3(PO4)3 simplified to AlPO4 ٣١ 9/13/2015 SAMPLE EXERCISE 2.9 Which of the following compounds would you expect to be ionic: N2O: Molecular Na2O: Ionic. CaCl2: Ionic SF4: Molecular Practice Exercise: Which of the following compounds are molecular: CBr4, FeS, P4O6, PbF2? Answer: CBr4 and P4O6 SAMPLE EXERCISE 2.10 What are the empirical formulas of the compounds formed by: (a) Al3+ and Cl– ions: AlCl3 (b) Al3+and O2– ions: Al2O3 (c) Mg2+and NO3–ions: Mg(NO3)2 Practice Exercise: Write the empirical formulas for the compounds formed by the following ions: (a) Na+and PO43–, (b) Zn2+and SO42–, (c) Fe3+and CO32–. Answer: a) Na3PO4 , (b) ZnSO4, (c) Fe2(CO3)3 ٣٢ 9/13/2015 COMMON CATIONS COMMON ANIONS ٣٣ 9/13/2015 CHEMISTRY AND LIFE: • Of the known elements, only about 29 are required for life. • Water accounts for at least 70% of the mass of most cells. • More than 97% of the mass of most organisms comprises just six elements (O, C, H, N, P and S). These are the most important elements for life • Carbon is the most common element in the solid components of cells. • The next most important ions are Na+, Mg2+, K+, Ca2+, and Cl– . • The other required 18 elements are only needed in trace amounts (green); they are trace elements. NAMING OF INORGANIC (NOMENCLATURE) Inorganic Compounds: 1- Ionic 2- Molecular COMPOUNDS 3- Acids and bases Naming Guide of Ionic Compounds: Write the name of the cation (same English name of neutral element) . If the anion is an element: change its ending to -ide; If the anion is a polyatomic ion: simply write the name of the polyatomic ion. If the cation can have more than one possible charge: write the charge as a Roman numeral in parentheses. ٣٤ 9/13/2015 NAMING IONIC COMPOUNDS Binary Ionic Compounds: 1) With Main Groups Metals: G 1A, 2A, and Al NaCl: Sodium Chloride MgO: Magnesium Oxide Al2O3: Aluminum Oxide 2) With Transition and Post Transition Metals: Use Roman numerals in parentheses to indicate the charge on metals that have more than one cation. Fe2O3 : Iron(III) Oxide SnCl2 : Tin(II) Chloride PbF2 : Lead(II) Fluoride Some transition metals form more than one cation ٣٥ 9/13/2015 PATTERNS IN OXYANION NOMENCLATURE Oxyanions: Polyatomic anions containing oxygen have names ending in either -ate or -ite . If two oxyanions involving the same element: The one with fewer oxygens ends in -ite. NO2− : nitrite SO32− : sulfite The one with more oxygens ends in -ate. SO42− : sulfate NO3− : nitrate For CO32-only one anion: carbonate For halogens 4 anions present: (Cl as an example) ClO4ClO3ClO2ClO- perchlorate ion chlorate ion chlorite ion hypochlorite ion (one more O atom than chlorate) (one O atom fewer than chlorate) (one O atom fewer than chlorite) Polyatomic anions containing oxygen with additional hydrogens: Anions from diprotic acids (H2CO3, H2SO3, H2SO4) CO32– carbonate anion. – HCO3 hydrogen carbonate (or bicarbonate) anion. HSO3hydrogen sulfite (or bisulfite) anion 2SO3 sulfite anion. HSO4 hydrogen sulfate (or bisulfate) anion SO42sulfate anion. Anions from polyprotic acids (H3PO4 ) PO43– phosphate ion. H2PO4– dihydrogen phosphate anion. 2– HPO4 hydrogen phosphate anion. ٣٦ 9/13/2015 ACID NOMENCLATURE Acids containing anions whose names end in -ide : Are named by changing the –ide ending to -ic, adding the prefix hydro- to this anion name, and then following with the word acid: FClBrIS2Se2CN- ٣٧ (fluoride) (chloride) (bromide) (iodide) (sulfide) (chloride) (cyanide) HCl(aq) (hydrochloric acid) HF (aq) (hydrofluric acid) HBr (aq) (hydrobromic acid) HI (aq) (hydroiodic acid) H2S( aq) (hydrosulfuric acid) HSe(aq ) (hydroselenic acid) HCN(aq ) (hydrocynic acid) 9/13/2015 Acids containing anions whose names end in -ate or –ite: are named by changing -ate to -ic and -ite to -ous and then adding the word acid. ClO4- (perchlorate) ClO3- (chlorate) ClO2- (chlorite) ClO- (hypochlorite) SO32- (sulfite) SO42- (sulfate) PO43- (phosphate) NO32- (nitrate) NO22- (nitrite) HClO4 HClO3 HClO2 HClO H2SO3 H2SO4 H3PO4 HNO3 HNO2 (perchloric acid) (chloric acid) (chlorous acid) (hypochlorous acid) (sulforous acid) (sulfuric acid) (phosphoric acid) (nitric acid) (nitrous acid) NOMENCLATURE OF BINARY MOLECULAR COMPOUNDS The less electronegative atom is usually listed first. A prefix is used to denote the number of atoms of each element in the compound (mono- is not used on the first element listed, however) . The ending on the more electronegative element is changed to -ide. Successive vowels are often elided into one. e.g. a and o→ o ٣٨ 9/13/2015 EXERCISE Cl2O NF3 N2O4 P4S10 CO CO2 P2O5 S2Cl4 NO2 N2O5 HCl(g) HI(l) N2Cl4 dichlorine monoxide nitrogen trifluoride dinitrogen tetroxide tetraphosphorus decasulfide carbon monoxide carbon dioxide diphosphorus pentoxide disulfur tetrachloride nitrogen dioxide dinitrogen penoxide hydrogen chloride gas hydrogen iodide liquid dinitrogen tetrachloride A base can be defined as a substance that yields hydroxide ions (OH-) when dissolved in water. ٣٩ NaOH sodium hydroxide KOH potassium hydroxide Ba(OH)2 barium hydroxide 9/13/2015 NAMING EXERCISE Al2(S2O3)3 P4O10 Cu(NO2)2 NaMnO4 CS2 Fe2(CrO4)3 KCl MgBr2 CaO CuBr FeS PbO2 SF6 N2 O 4 Aluminum thiosulfate Tetraphosphorous decaoxide Copper(II) nitrite Sodium permanganate Carbon disulfide Iron(III) chromate Potassium chloride Magnesium bromide Calcium oxide Copper(I) bromide Iron(II) sulfide Lead(IV) oxide Sulfur hexafluoride Dinitrogen tetroxide NOMENCLATURE OF ORGANIC COMPOUNDS Organic chemistry is the study of carbon. Organic chemistry has its own system of nomenclature. The simplest hydrocarbons (compounds containing only carbon and hydrogen) are alkanes. The first part of the names above correspond to the number of carbons (meth- = 1, eth- = 2, prop- = 3, etc.). ٤٠ 9/13/2015 When a hydrogen in an alkane is replaced with something else (a functional group, like -OH in the compounds above), the name is derived from the name of the alkane. The ending denotes the type of compound. An alcohol ends in -ol. 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