Dalton's Atomic Theory (1808) PDF

9/9/2024 Dalton’s Atomic Theory (1808) 1. Elements are composed of extremely small particles called atoms. 2. All atoms of a given element are identical, having the same size, mass and chemical properties. The atoms of one element are different from the atoms of a...

9/9/2024 Dalton’s Atomic Theory (1808) 1. Elements are composed of extremely small particles called atoms. 2. All atoms of a given element are identical, having the same size, mass and chemical properties. The atoms of one element are different from the atoms of all other elements. 3. Compounds are composed of atoms of more than one element. In any compound, the ratio of the numbers of atoms of any two of the elements present is either an integer or a simple fraction. 4. A chemical reaction involves only the separation, combination, or rearrangement of atoms; it does not result in their creation or destruction. 2 2 Dalton’s Atomic Theory Law of Multiple Proportions 3 3 1  9/9/2024 Law of Conservation of Mass 16 X 8Y → 8X Y 4 4 Cathode Ray Tube J.J. Thomson, measured mass/charge of e (1906 Nobel Prize in Physics) 5 5 2  9/9/2024 Cathode Ray Tube (1) 6 6 Millikan’s Experiment Measured mass of e (1923 Nobel Prize in Physics) e charge 1.60 10 C Thompson s charge⁄mass of e 1.76 10 C⁄g e mass 9.10 10 g 7 7 3  9/9/2024 Types of Radioactivity (uranium compound) 8 8 Thomson’s Model 9 9 4  9/9/2024 Rutherford’s Experiment (1908 Nobel Prize in Chemistry) ∝ particle velocity ~ 1.4 10 m⁄s ~5% speed of light 1. atoms positive charge is concentrated in the nucleus 2. proton (p) has opposite (+) charge of electron (-) 3. mass of p is 1840 mass of e 1.67 10 g 10 10 Rutherford’s Model of the Atom atomic radius ~ 100 pm 1 10 m nuclear radius ~ 5 10 pm 5 10 m “If the atom is the Houston Astrodome, then the nucleus is a marble on the 50-yard line.” 11 11 5  9/9/2024 Chadwick’s Experiment (1932) (1935 Noble Prize in Physics) H atoms: 1 p; He atoms: 2 p mass He/mass H should = 2 measured mass He/mass H = 4 ∝ 9Be → 1n 12C energy neutron (n) is neutral charge 0 n mass ~ p mass 1.67 10 g 12 12 Properties of Subatomic Particles Copyright © McGraw-Hill Education. 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Table 2.1 Mass and Charge of Subatomic Particles Particle Mass (g) Coulomb Charge Unit Charge Charge Electron* 9.10938 10 1.6022 10 1 Proton 1.67262 10 1.6022 10 1 Neutron 1.67493 10 0 0 *More refined measurements have given us a more accurate value of an electron's mass than Millikan's. mass p mass n 1840 mass e 13 13 6  9/9/2024 Atomic Number, Mass Number, and Isotopes Atomic number (Z) = number of protons in nucleus Mass number (A) = number of protons + number of neutrons = atomic number (Z) + number of neutrons Isotopes are atoms of the same element (X) with different numbers of neutrons in their nuclei Mass Number → Atomic Number → X ← Element Symbol H H D H T U U 14 14 The Isotopes of Hydrogen 15 15 7  9/9/2024 Example 2.1 Give the number of protons, neutrons, and electrons in each of the following species: 20 (a) Na 11 22 (b) Na 11 (c) 17O (d) carbon-14 16 Example 2.1 (1) Strategy Recall that the superscript denotes the mass number (A) and the subscript denotes the atomic number (Z). Mass number is always greater than atomic number. (The only exception is H, where the mass number is equal to the atomic number.) In a case where no subscript is shown, as in parts (c) and (d), the atomic number can be deduced from the element symbol or name. To determine the number of electrons, remember that because atoms are electrically neutral, the number of electrons is equal to the number of protons. 17 8  9/9/2024 Example 2.1 (2) Solution (a) Na The atomic number is 11, so there are 11 protons. The mass number is 20, so the number of neutrons is 20 – 11= 9. The number of electrons is the same as the number of protons; that is, 11. (b) Na The atomic number is the same as that in (a), or 11. The mass number is 22, so the number of neutrons is 22 − 11 = 11. The number of electrons is 11. Note that the species in (a) and (b) are chemically similar isotopes of sodium. 18 Example 2.1 (3) (c) 17O The atomic number of O (oxygen) is 8, so there are 8 protons. The mass number is 17, so there are 17 8 9 neutrons. There are 8 electrons. (d) Carbon-14 can also be represented as 14C. The atomic number of carbon is 6, so there are 14 6 8 neutrons. The number of electrons is 6. 19 9  9/9/2024 The Modern Periodic Table Alkali Metal Halogen Noble Gas Alkali Earth Metal Group Period 20 20 Chemistry In Action Natural abundance of elements in Earth’s crust: Natural abundance of elements in human body: 21 21 10  9/9/2024 Molecules A molecule is an aggregate of two or more atoms in a definite arrangement held together by chemical forces. A diatomic molecule contains only two atoms: H2, N2, O2, BR2, HCl, CO diatomic elements A polyatomic molecule contains more than two atoms: O3, H2O, NH3, CH4 22 22 Ions An ion is an atom, or group of atoms, that has a net positive or negative charge. cation – ion with a positive charge If a neutral atom loses one or more electrons it becomes a cation. 11 protons 11 protons Na 11 electrons Na 10 electrons anion – ion with a negative charge If a neutral atom gains one or more electrons it becomes an anion. 17 protons 17 protons Cl 17 electrons Cl 18 electrons 23 23 11  9/9/2024 Types of Ions A monatomic ion contains only one atom: Na , Cl , Ca , O , Al , N A polyatomic ion contains more than one atom: OH , CN , NH , NO 24 24 Common Ions Shown on the Periodic Table 25 25 12  9/9/2024 Formulas and Models 26 26 Types of Formulas A molecular formula shows the exact number of atoms of each element in the smallest unit of a substance. An empirical formula shows the simplest whole-number ratio of the atoms in a substance. molecular empirical H O H O C H O CH O O O N H NH 27 27 13  9/9/2024 Example 2.2 Write the molecular formula of methylamine, an organic solvent, from its ball-and-stick model, shown below. 28 Example 2.2 (1) Solution Refer to the labels (also see back endpapers). There are four H atoms, one C atom, and one O atom. Therefore, the molecular formula is CH O. However, the standard way of writing the molecular formula for methanol is CH OH because it shows how the atoms are joined in the molecule. 29 14  9/9/2024 Example 2.3 Write the empirical formulas for the following molecules: (a)acetylene C H , which is used in welding torches (b)glucose C H O , a substance known as blood sugar (c)nitrous oxide N O , a gas that is used as an anesthetic gas (“laughing gas”) and as an aerosol propellant for whipped creams. 30 Example 2.3 (1) Strategy Recall that to write the empirical formula, the subscripts in the molecular formula must be converted to the smallest possible whole numbers. 31 15  9/9/2024 Example 2.3 (2) Solution (a) There are two carbon atoms and two hydrogen atoms in acetylene. Dividing the subscripts by 2, we obtain the empirical formula CH. (b) In glucose there are 6 carbon atoms, 12 hydrogen atoms, and 6 oxygen atoms. Dividing the subscripts by 6, we obtain the empirical formula CH O. Note that if we had divided the subscripts by 3, we would have obtained the formula C H O. Although the ratio of carbon to hydrogen to oxygen atoms in C H O is the same as that in C H O (1:2:1), C H O is not the simplest formula because its subscripts are not in the smallest whole-number ratio. 32 Example 2.3 (3) (c) Because the subscripts in N O are already the smallest possible whole numbers, the empirical formula for nitrous oxide is the same as its molecular formula. 33 16  9/9/2024 Ionic Compounds Ionic compounds consist of a combination of cations and anions. The formula is usually the same as the empirical formula. The sum of the charges on the cation(s) and anion(s) in each formula unit must equal zero. The ionic compound NaCl 34 34 Reactive Elements The most reactive metals (green) and the most reactive nonmetals (blue) combine to form ionic compounds. 35 35 17  9/9/2024 Formulas of Ionic Compounds 2x 3 6 3 2 6 Al O Al O 1 2 2 2 1 2 CaBr Ca Br 2 1 2 1 2 2 Na CO Na CO 2 36 36 Example 2.4 Write the formula of magnesium nitride, containing the Mg and N ions. When magnesium burns in air, it forms both magnesium oxide and magnesium nitride. 37 18  9/9/2024 Example 2.4 (1) Strategy Our guide for writing formulas for ionic compounds is electrical neutrality; that is, the total charge on the cation(s) must be equal to the total charge on the anion(s). Because the charges on the Mg and N ions are not equal, we know the formula cannot be MgN. Instead, we write the formula as Mg N , where x and y are subscripts to be determined. 38 Example 2.4 (2) Solution To satisfy electrical neutrality, the following relationship must hold: 2 𝑋 3 𝑌 0 Solving, we obtain 𝑋⁄𝑌 3⁄2. Setting 𝑋 3 and 𝑌 2, we write Check The subscripts are reduced to the smallest whole- number ratio of the atoms because the chemical formula of an ionic compound is usually its empirical formula. 39 19  9/9/2024 Chemical Nomenclature Ionic Compounds – Often a metal + nonmetal – Anion (nonmetal), add “-ide” to element name BaCl barium chloride K O potassium oxide Mg OH magnesium hydroxide KNO potassium nitrate 40 40 Naming Transition Metal Ionic Compounds Transition metal ionic compounds – indicate charge on metal with Roman numerals FeCl 2Cl 2 so Fe is 2 iron(II) chloride FeCl 3Cl 3 so Fe is 3 iron(III) chloride Cr S 3S 6 so Cr is 3 6⁄2 chromium(III) sulfide 41 41 20  9/9/2024 Naming Monatomic Anions Copyright © McGraw-Hill Education. Permission required for reproduction or display. Table 2.2 The "-ide" Nomenclature of Some Common Monatomic Anions According to Their Positions in the Periodic Table Group 4A Group 5A Group 6A Group 7A C carbide C * N nitride N O oxide O F fluoride F Si silicide Si P phosphide P S sulfide S CI chloride Cl Se selenide Se Br bromide Br Te telluride Te I iodide I *The word "carbide" is also used for the anion Cl. 42 42 Common Inorganic Ions Copyright © McGraw-Hill Education. Permission required tor reproduction or display. Table 2.3 Names and Formulas of Some Common Inorganic Cations and Anions Cation Anion aluminum Al bromide Br ammonium NH carbonate CO barium Ba chlorate ClO cadmium Cd chloride Cl calcium Ca chromate CrO cesium Cs cyanide CN chromium(III) or chromic Cr dichromate Cr O cobalt(U) or cobaltous Co dihydrogen phosphate H PO copper(I) or cuprous Cu fluoride F copper(II) or cupric Cu hydride H hydrogen H hydrogen carbonate or bicarbonate HCO iron(II) or ferrous Fe hydrogen phosphate HPO iron(lll) or ferric Fe hydrogen sulfate or bisulfatc HSO lead(II) or plumbous Pb hydroxide OH lithium Li iodide I magnesium Mg nitrate NO manganesc(II) or mangauous Mn nitride N mcrcury(I) or mercurous Hg * nitrite NO mcrcury(II) or mercuric Hg oxide O potassium K permanganate MnO rubidium Rb peroxide O silver Ag phosphate PO sodium Na sulfate SO strontium Sr sulfide S tin(II) or stannous Sn sulfite SO zinc Zn thiocyanate SCN 43 *The word "carbide" is also used for the anion C. 43 21  9/9/2024 Example 2.5 Name the following compounds: a Cu NO 2 (b) KH2PO c NH ClO 44 Example 2.5 (1) Strategy Note that the compounds in (a) and (b) contain both metal and nonmetal atoms, so we expect them to be ionic compounds. There are no metal atoms in (c) but there is an ammonium group, which bears a positive charge. So NH ClO is also an ionic compound. Our reference for the names of cations and anions is Table 2.3. Keep in mind that if a metal atom can form cations of different charges (see Figure 2.11), we need to use the Stock system. 45 22  9/9/2024 Example 2.5 (2) Solution (a) The nitrate ion NO bears one negative charge, so the copper ion must have two positive charges. Because copper forms both Cu and Cu ions, we need to use the Stock system and call the compound copper(II) nitrate. (b) The cation is K and the anion is H PO (dihydrogen phosphate). Because potassium only forms one type of ion K , there is no need to use potassium(I) in the name. The compound is potassium dihydrogen phosphate. (c) The cation is NH (ammonium ion) and the anion is ClO. The compound is ammonium chlorate. 46 Example 2.6 Write chemical formulas for the following compounds: (a) mercury(I) nitrite (b) cesium sulfide (c) calcium phosphate 47 23  9/9/2024 Example 2.6 (1) Strategy We refer to Table 2.3 for the formulas of cations and anions. Recall that the Roman numerals in the Stock system provide useful information about the charges of the cation. 48 Example 2.6 (2) Solution (a) The Roman numeral shows that the mercury ion bears a 1 charge. According to Table 2.3, however, the mercury(I) ion is diatomic (that is, Hg and the nitrite ion is NO. Therefore, the formula is Hg NO. (b) Each sulfide ion bears two negative charges, and each cesium ion bears one positive charge (cesium is in Group 1A, as is sodium). Therefore, the formula is Cs S. 49 24  9/9/2024 Example 2.6 (3) (c) Each calcium ion Ca bears two positive charges, and each phosphate ion PO bears three negative charges. To make the sum of the charges equal zero, we must adjust the numbers of cations and anions: 3 2 2 3) 0 Thus, the formula is Ca PO 2. 50 Molecular Compounds Molecular compounds Copyright © McGraw-Hill Education. Permission required tor reproduction or display. Table 2.4 − Nonmetals or nonmetals + metalloids Greek Prefixes Used in Naming Molecular − Common names Compounds Prefix Meaning − H O, NH , CH mono‐ 1 − Element furthest to the left in a period di‐ 2 and closest to the bottom of a group on tri‐ 3 periodic table is placed first in formula tetra‐ 4 penta‐ 5 − If more than one compound can be hexa‐ 6 formed from the same elements, use hepta‐ 7 prefixes to indicate number of each octa‐ 8 kind of atom nona‐ 9 − Last element name ends in -ide deca‐ 10 51 51 25  9/9/2024 Examples of Molecular Compounds Hl hydrogen iodide NF nitrogen trifluoride SO sulfur dioxide N Cl dinitrogen tetrachloride NO nitrogen dioxide N O dinitrogen monoxide 52 52 Example 2.7 Name the following molecular compounds: a SiCl b PO 53 26  9/9/2024 Example 2.7 (1) Strategy We refer to Table 2.4 for prefixes. In (a) there is only one Si atom so we do not use the prefix “mono.” Solution (a)Because there are four chlorine atoms present, the compound is silicon tetrachloride. (b)There are four phosphorus atoms and ten oxygen atoms present, so the compound is tetraphosphorus decoxide. Note that the “a” is omitted in “deca.” 54 Example 2.8 Write chemical formulas for the following molecular compounds: (a) carbon disulfide (b) disilicon hexabromide 55 27  9/9/2024 Example 2.8 (1) Strategy Here we need to convert prefixes to numbers of atoms (see Table 2.4). Because there is no prefix for carbon in (a), it means that there is only one carbon atom present. Solution (a) Because there are two sulfur atoms and one carbon atom present, the formula is CS. (b) There are two silicon atoms and six bromine atoms present, so the formula is Si Br. 56 Flowchart for Naming Compounds 57 57 28  9/9/2024 Acids An acid can be defined as a substance that yields hydrogen ions H when dissolved in water. For example: HCl gas and HCl in water Pure substance, hydrogen chloride Dissolved in water (H O and Cl ), hydrochloric acid 58 58 Some Simple Acids Copyright © McGraw-Hill Education. Permission required for reproduction or display. Table 2.5 Some Simple Acids Acid Corresponding Anion HF (hydrofluoric acid) F (fluoride) HCl (hydrochloric acid) Cl (chloride) HBr (hydrobromic acid) Br (bromide) HI (hydroiodic acid) I (iodide) HCN (hydrocyanic acid) CN (cyanide) H S (hydrosulfuric acid) S (sulfide) 59 59 29  9/9/2024 Oxoacids An oxoacid is an acid that contains hydrogen, oxygen, and another element. HNO nitric acid H CO carbonic acid H PO phosphoric acid 60 60 Naming Oxoacids and Oxoanions 61 61 30  9/9/2024 Naming Oxoanions The rules for naming oxoanions, anions of oxoacids, are as follows: 1. When all the H ions are removed from the “-ic” acid, the anion’s name ends with “-ate.” 2. When all the H ions are removed from the “-ous” acid, the anion’s name ends with “-ite.” 3. The names of anions in which one or more but not all the hydrogen ions have been removed must indicate the number of H ions present. For example: – H PO dihydrogen phosphate – HPO hydrogen phosphate – PO phosphate 62 62 Chlorine-Containing Oxoacids and Oxoanions Copyright © McGraw-Hill Education. Permission required for reproduction or display. Table 2.6 Names of Oxoacids and Oxoanions That Contain Chlorine Acid Corresponding Anion HClO (perchloric acid) ClO (perchlorate) HClO (chloric acid) ClO (chlorate) HClO (chlorous acid) ClO (chlorite) HClO (hypochlorous acid) ClO (hypochlorite) 63 63 31  9/9/2024 Example 2.9 Name the following oxoacid and oxoanion: a H PO (b) IO 64 Example 2.9 (1) Strategy To name the acid in (a), we first identify the reference acid, whose name ends with “ic,” as shown in Figure 2.15. In (b), we need to convert the anion to its parent acid shown in Table 2.6. Solution (a)We start with our reference acid, phosphoric acid H PO. Because H PO has one fewer O atom, it is called phosphorous acid. (b)The parent acid is HIO. Because the acid has one more O atom than our reference iodic acid HIO , it is called periodic acid. Therefore, the anion derived from HIO is called periodate. 65 32  9/9/2024 Bases A base can be defined as a substance that yields hydroxide ions OH when dissolved in water. NaOH sodium hydroxide KOH potassium hydroxide Ba OH 2 barium hydroxide 66 66 Hydrates Hydrates are compounds that have a specific number of water molecules attached to them. BaCl · 2H O barium chloride dihydrate LiCl · H O lithium chloride monohydrate MgSO · 7H O magnesium sulfate heptahydrate Sr NO 2 ·4H O strontium nitrate tetrahydrate CuSO · 5H O → ← CuSO 67 67 33  9/9/2024 Common and Systematic Names of Compounds Copyright© McGraw-Hill Education. Permission required for reproduction or display. Table 2.7 Common and Systematic Names of Some Compounds Formula Common Name Systematic Name H O Water Dihydrogen monoxide NH Ammonia Trihydrogen nitride CO Dry ice Solid carbon dioxide NaCl Table salt Sodium chloride N O Laughing gas Dinitrogen monoxide CaCO Marble, chalk, limestone Calcium carbonate CaO Quicklime Calcium oxide Ca OH Slaked lime Calcium hydroxide NaHCO Baking soda Sodium hydrogen carbonate Na CO. 10H O Washing soda Sodium carbonate decahydrate MgSO. 7H O Epsom salt Magnesium sulfate heptahydrate Mg OH Milk of magnesia Magnesium hydroxide CaSO. 2H O Gypsum Calcium sulfate dehydrate 68 68 Organic Chemistry Organic chemistry is the branch of chemistry that deals with carbon compounds. Functional Groups: H H H O H C OH H C NH2 H C C OH H H H methanol methylamine acetic acid 69 69 34  9/9/2024 Ten Straight-Chain Alkanes 70 70 35