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Unformatted text preview: Chemistry 1110/1210 Dr Eric E. Moore Section 2.1 Chemical Formulas Section 2.2 Chemical Equations Section 2.3 Energy Section 2.4 Molecular Compounds Section 2.5 Naming Compounds Section 2.6 Ionic Compounds Section 2.7 Ionic Formulas Section 2.8 Naming Ionic Compounds Section 2.9 Properties of Compounds Chemistry 1110/1210 Dr Eric E. Moore Section 2.1 Chemical Formulas Section 2.2 Chemical Equations Section 2.3 Energy 1 Section 2.1 Chemical Formulas 2 Section 2.2 Chemical Equations 3 Section 2.3 Energy 4 Section 2.4 Molecular Compounds 5 Section 2.5 Naming Compounds 6 Section 2.6 Ionic Compounds 7 Section 2.7 Ionic Formulas 8 Section 2.8 Naming Ionic Compounds 9 Section 2.9 Properties of Compounds Chemistry 1110/1210 Chapter 2 Dr Eric E. Moore St John's University Section 2.4 Molecular Compounds Section 2.5 Naming Compounds Section 2.6 Ionic Compounds Section 2.7 Ionic Formulas Section 2.8 Naming Ionic Compounds Section 2.9 Properties of Compounds September 9, 2007 Chemistry 1110/1210 Dr Eric E. Moore Section 2.1 Chemical Formulas Section 2.2 Chemical Equations Section 2.3 Energy Section 2.4 Molecular Compounds Section 2.5 Naming Compounds Section 2.6 Ionic Compounds Section 2.7 Ionic Formulas Section 2.8 Naming Ionic Compounds Section 2.9 Properties of Compounds Chemical Formulas Chemistry 1110/1210 Dr Eric E. Moore Section 2.1 Chemical Formulas Hydrates Some compounds form special complexes with water. For example, a molecule of Calcium Sulfate (CaSO4 ) can "grab hold of" two water molecules. These water molecules are attached/attracted more strongly than the molecules in a mixture of water and something else, but less strongly than the atoms in a compound. Such a complex is known as a "Hydrate". In a hydrate, the additional water molecules are shown after a dot: CaSO4 2H2 O Says that each Calcium Sulfate molecule is associated with two water molecules. A little more on chemical formulas. If the atom occurs just once in a compound (like the Oxygen in H2 O), then it appears without a subscript (i.e. we don't use subscript ones (H2 O1 ). Sometimes, we don't just count atoms, but use parentheses to indicate structural information. e.g. CO(NH2 )2 or Ca(NO3 )2 The formulas for these molecules could be shown as CON2 H4 and CaN2 O6 , but the other formula tells us more about the structure of the compound (what exactly, we will discuss later). Section 2.2 Chemical Equations Section 2.3 Energy Section 2.4 Molecular Compounds Section 2.5 Naming Compounds Section 2.6 Ionic Compounds Section 2.7 Ionic Formulas Section 2.8 Naming Ionic Compounds Section 2.9 Properties of Compounds Chemistry 1110/1210 Dr Eric E. Moore Section 2.1 Chemical Formulas Section 2.2 Chemical Equations Section 2.3 Energy Section 2.4 Molecular Compounds Section 2.5 Naming Compounds Section 2.6 Ionic Compounds Section 2.7 Ionic Formulas Section 2.8 Naming Ionic Compounds Section 2.9 Properties of Compounds Counting Atoms It's important to be able to count the number of atoms of each element in a molecule even for ones with the "weirder" formulas. For example take Co(NO3 )2 6H2 O. For each molecule of this compound, there are: One Cobalt (Co) atom. Two Nitrogen (N) atoms Chemistry 1110/1210 Dr Eric E. Moore Section 2.1 Chemical Formulas Section 2.2 Chemical Equations Section 2.3 Energy Section 2.4 Molecular Compounds Section 2.5 Naming Compounds Section 2.6 Ionic Compounds Section 2.7 Ionic Formulas Section 2.8 Naming Ionic Compounds Section 2.9 Properties of Compounds Chemical Equations Chemical equations describe what happens during a chemical reaction. The reactants are on the left. An arrow separates the reactants from the products The products are on the right of the arrow If more than one molecule is reacting, the number of molecules reacting is shown as a number (a "coefficient") before the molecule's formula The state (solid (s), liquid (l ), gas (g ), aqueous (aq)) can be shown in parentheses after the formula (usually italicized in print). 2 C(s) + O2 (g ) 2 CO(g ) Since there are two NO3 subgroups (the two outside the parentheses), each one of which has one nitrogen. Twelve Oxygen (O) atoms The NO3 's each have 3, and there's two NO3 's, which means they have a total of six, and the six waters have another six oxygens. Twelve Hydrogen (H) atoms Each water in the hydrate has two, and there's six waters. Chemistry 1110/1210 Dr Eric E. Moore Section 2.1 Chemical Formulas Section 2.2 Chemical Equations Section 2.3 Energy Section 2.4 Molecular Compounds Section 2.5 Naming Compounds Section 2.6 Ionic Compounds Section 2.7 Ionic Formulas Section 2.8 Naming Ionic Compounds Section 2.9 Properties of Compounds Energy Chemistry 1110/1210 Dr Eric E. Moore Section 2.1 Chemical Formulas Energy of molecules "Energy" is the capacity to make things move. "Kinetic Energy" is the energy something that's already moving around has. "Potential Energy" is energy that's stored somehow, and ready to make something move. Energy is conserved, like atoms, it is never created or destroyed. It can be converted from kinetic to potential energy and back again, or from one place/thing to another, but never created or destroyed. Section 2.2 Chemical Equations Section 2.3 Energy Section 2.4 Molecular Compounds Section 2.5 Naming Compounds Section 2.6 Ionic Compounds Section 2.7 Ionic Formulas Section 2.8 Naming Ionic Compounds Section 2.9 Properties of Compounds The "Temperature" of a bunch of molecules is a measure of the average kinetic energy of those molecules. "Heat" is the total amount of kinetic energy added to or removed from a bunch of molecules. Chemistry 1110/1210 Dr Eric E. Moore Section 2.1 Chemical Formulas Section 2.2 Chemical Equations Section 2.3 Energy Section 2.4 Molecular Compounds Section 2.5 Naming Compounds Section 2.6 Ionic Compounds Section 2.7 Ionic Formulas Section 2.8 Naming Ionic Compounds Section 2.9 Properties of Compounds Energy of reactions Chemistry 1110/1210 Dr Eric E. Moore Section 2.1 Chemical Formulas Section 2.2 Chemical Equations Section 2.3 Energy Section 2.4 Molecular Compounds Section 2.5 Naming Compounds Section 2.6 Ionic Compounds Section 2.7 Ionic Formulas Section 2.8 Naming Ionic Compounds Section 2.9 Properties of Compounds Nonmetallic compounds Some reactions release energy (e.g. burning charcoal). When they do, the energy usually is converted into heat, which raises the temperature of the products. This energy had to come from somewhere. The only really workable explanation is that it was stored as potential energy in the bonds that hold a molecule together, and that when we re-arranged the molecules, it was released. Nonmetals can combine in a variety of ways. Many form compounds with hydrogen (CH4 , NH3 , H2 O, HF). The compounds they form depends on what period (column of the periodic table) they're in. Chemistry 1110/1210 Dr Eric E. Moore Section 2.1 Chemical Formulas Section 2.2 Chemical Equations Section 2.3 Energy Section 2.4 Molecular Compounds Section 2.5 Naming Compounds Section 2.6 Ionic Compounds Section 2.7 Ionic Formulas Section 2.8 Naming Ionic Compounds Section 2.9 Properties of Compounds Organic Chemistry Carbon forms a bewildering array of compounds. So many, that the chemistry of carbon compounds has a special name, "Organic Chemistry". The reason it forms so many compounds is that it bonds well to itself. The simplest class of organic compounds is the "Alkanes" Alkanes have chemical formulas of the form Cn H2n+2 . Alkanes have special names. For n=1-10 they are Methane, Ethane, Propane, Butane, Pentane, Hexane, Heptane, Octane, Nonane, Decane. Other organic molecules have names based off the names of the Alkanes, for example alcohols have the ending -ol: Methanol, Ethanol, Propanol, etc. Chemistry 1110/1210 Dr Eric E. Moore Section 2.1 Chemical Formulas Section 2.2 Chemical Equations Section 2.3 Energy Section 2.4 Molecular Compounds Section 2.5 Naming Compounds Section 2.6 Ionic Compounds Section 2.7 Ionic Formulas Section 2.8 Naming Ionic Compounds Section 2.9 Properties of Compounds Kinds of Compounds There's two basic kinds of compounds: "Molecular compounds", which are usually formed of two (or more) nonmetals, and "Ionic compounds", which are formed from a metal and nonmetal. Compounds can be "binary" (containing two different kinds of atoms, like HCl or SF6 ). Molecular compounds can also be "diatomic" (containing two atoms, possibly the same kind, like HCl or O2 ). Chemistry 1110/1210 Dr Eric E. Moore Section 2.1 Chemical Formulas Section 2.2 Chemical Equations Section 2.3 Energy Section 2.4 Molecular Compounds Section 2.5 Naming Compounds Section 2.6 Ionic Compounds Section 2.7 Ionic Formulas Section 2.8 Naming Ionic Compounds Section 2.9 Properties of Compounds Naming diatomic binary molecular compounds Just a few simple rules will allow you to name these compounds: 1 2 3 Chemistry 1110/1210 Dr Eric E. Moore Section 2.1 Chemical Formulas Section 2.2 Chemical Equations Section 2.3 Energy Section 2.4 Molecular Compounds Section 2.5 Naming Compounds Section 2.6 Ionic Compounds Section 2.7 Ionic Formulas Section 2.8 Naming Ionic Compounds Section 2.9 Properties of Compounds Naming polyatomic binary molecular compounds "Polyatomic" molecules are those containing more than two atoms. If there's more than one of some kind of atom, use greek prefixes to indicate how many. For example: CO2 is Carbon dioxide. CO is Carbon monoxide. PBr3 is Phosphorus tribromide. N2 O4 is Dinitrogen tetroxide Put the name of the first element first. Then the name of the second element With the ending replaced by "-ide" For example to name HCl: Hydrogen Chlorine For example to name HBr: Hydrogen Bromine The greek prefixes we most often encounter are mono-, di-, tri-, tetra-, penta-, and hexa-. Prefixes ending in a- or o- often drop the vowel when put before another vowel (hence tetroxide rather than tetraoxide). Chemistry 1110/1210 Dr Eric E. Moore Section 2.1 Chemical Formulas Section 2.2 Chemical Equations Section 2.3 Energy Section 2.4 Molecular Compounds Section 2.5 Naming Compounds Section 2.6 Ionic Compounds Section 2.7 Ionic Formulas Section 2.8 Naming Ionic Compounds Section 2.9 Properties of Compounds Ionic Compounds Chemistry 1110/1210 Dr Eric E. Moore Section 2.1 Chemical Formulas Section 2.2 Chemical Equations Section 2.3 Energy Section 2.4 Molecular Compounds Section 2.5 Naming Compounds Section 2.6 Ionic Compounds Section 2.7 Ionic Formulas Section 2.8 Naming Ionic Compounds Section 2.9 Properties of Compounds Ionic Compounds The individual ions pack themselves into a crystal lattice. They don't associate in "pairs" like the atoms in a diatomic molecule, but they do form an overall neutral structure. When metals react with nonmetals, they frequently form "Ionic Compounds", which are compounds formed out of two "Ions". An Ion is a charged molecule (or something that would be a molecule, if it were not charged). When the nonmetal and metal react, the atom of the metal loses one or more electrons to produce a positively charged ion, and the nonmetal gains the electrons to produce a negatively charged ion. The two ions produced are attracted to one another, and (usually) pack themselves together into a regular crystalline (solid) structure. The formula for the ionic compound is the "simplest" formula which is charge-neutral. This is called the "formula unit". Chemistry 1110/1210 Dr Eric E. Moore Section 2.1 Chemical Formulas Section 2.2 Chemical Equations Section 2.3 Energy Section 2.4 Molecular Compounds Section 2.5 Naming Compounds Section 2.6 Ionic Compounds Section 2.7 Ionic Formulas Section 2.8 Naming Ionic Compounds Section 2.9 Properties of Compounds Ions Chemistry 1110/1210 Dr Eric E. Moore Section 2.1 Chemical Formulas Oxidation States When an atom or molecule loses (gains) an electron, we describe that as the atom or molecule being "Oxidized" ("Reduced"). Thus, we refer to the charge of an ion as it's "Oxidation State". The oxidation state of an ion is shown as a superscript above and to the right of the label of the atom (or in some cases, molecule), e.g. Na+ (or Na+1 ), Ca2+ , O2- , or F- . Positively charged ions (oxidation state +1 or greater) are called "Cations" (usually metals) and negatively charged ions are called "Anions". Section 2.2 Chemical Equations Section 2.3 Energy Section 2.4 Molecular Compounds Section 2.5 Naming Compounds Section 2.6 Ionic Compounds Section 2.7 Ionic Formulas Section 2.8 Naming Ionic Compounds Section 2.9 Properties of Compounds Some elements have characteristic oxidation states that they are usually found in (besides the neutral 0 oxidation state). For example, the group 1A elements (the first column of the periodic table, Li, Na, K, ...) form ions with the oxidation state +1. Chemistry 1110/1210 Dr Eric E. Moore Section 2.1 Chemical Formulas Section 2.2 Chemical Equations Section 2.3 Energy Section 2.4 Molecular Compounds Section 2.5 Naming Compounds Section 2.6 Ionic Compounds Section 2.7 Ionic Formulas Section 2.8 Naming Ionic Compounds Section 2.9 Properties of Compounds Characteristic Oxidation States The characteristic oxidation states of some important elements: the group 1A elements (the first column of the periodic Chemistry 1110/1210 Dr Eric E. Moore Section 2.1 Chemical Formulas Section 2.2 Chemical Equations Section 2.3 Energy Section 2.4 Molecular Compounds Section 2.5 Naming Compounds Section 2.6 Ionic Compounds Section 2.7 Ionic Formulas Section 2.8 Naming Ionic Compounds Section 2.9 Properties of Compounds Formulas of Ionic Compounds table, Li, Na, K, ...) form ions with the oxidation state +1. (The "Alkali Metals") the group 2A elements (the second column of the periodic table, Be, Mg, Ca, ...) form ions with the oxidation state +2. (The "Alkaline Earth Metals") the group 4A elements C, Si) form ions with the oxidation state -4. the group 5A elements N, P) form ions with the oxidation state -3. the group 6A elements O, S, ...) form ions with the oxidation state -2. the group 7A elements F, Cl, ...) form ions with the oxidation state -1. (The "Halogens"). The formula of many ionic compounds can be predicted from their characteristic oxidation states. For example, since Calcium (Ca, an alkaline earth metal) forms ions in the +2 oxidation state, and Fluorine (F, a halogen) forms ions in the -1 oxidation state, to be neutral, the formula unit has to have twice as many fluorine atoms as calcium atoms. Thus, the formula unit is CaF2 . Note that the ions are not written with their charges, this is not because they lose the charge in the compound, just because we omit them because they're implied. Chemistry 1110/1210 Dr Eric E. Moore Section 2.1 Chemical Formulas Section 2.2 Chemical Equations Section 2.3 Energy Section 2.4 Molecular Compounds Section 2.5 Naming Compounds Section 2.6 Ionic Compounds Section 2.7 Ionic Formulas Section 2.8 Naming Ionic Compounds Section 2.9 Properties of Compounds Transition Metal Oxidation States Chemistry 1110/1210 Dr Eric E. Moore Section 2.1 Chemical Formulas Polyatomic Ions Transition metals often form ions of two (or occasionally more) different oxidation states. For example, Iron can form ions with charge +2 or +3. For these ions, you need to know what oxidation state they're in to predict the formula unit of the ionic compound that they form. For example, iron forms two compounds, if the iron goes into the Fe2+ state, it forms the compound FeO with oxygen, but if it goes into the Fe3+ oxidation state, it forms the compound Fe2 O3 . Section 2.2 Chemical Equations Section 2.3 Energy Section 2.4 Molecular Compounds Section 2.5 Naming Compounds Section 2.6 Ionic Compounds Section 2.7 Ionic Formulas Section 2.8 Naming Ionic Compounds Section 2.9 Properties of Compounds There are many non-binary ionic compounds. These are frequently due to the inclusion of a "Polyatomic Ion". A polyatomic ion is basically a molecule with a charge. The uncharged form of the ion usually doesn't actually exist as a molecule, but like a molecule the atoms remain in a fixed relation to one another. Most polyatomic ions are anions (negatively charged). Some common polyatomic ions are ammonium (NH+ ), sulfate 4 (SO2- ), nitrate (NO- ), acetate (C2 H5 O- ), and carbonate 2 3 4 (CO2- ). 3 Chemistry 1110/1210 Dr Eric E. Moore Section 2.1 Chemical Formulas Section 2.2 Chemical Equations Section 2.3 Energy Section 2.4 Molecular Compounds Section 2.5 Naming Compounds Section 2.6 Ionic Compounds Section 2.7 Ionic Formulas Section 2.8 Naming Ionic Compounds Section 2.9 Properties of Compounds Naming Ionic Compounds Ionic compounds are named pretty much the same way as non-ionic/molecular compounds, with a few exceptions. Some new rules that matter with ionic compounds: Since the formula can usually be predicted, don't use the Chemistry 1110/1210 Dr Eric E. Moore Section 2.1 Chemical Formulas Section 2.2 Chemical Equations Section 2.3 Energy Section 2.4 Molecular Compounds Section 2.5 Naming Compounds Section 2.6 Ionic Compounds Section 2.7 Ionic Formulas Section 2.8 Naming Ionic Compounds Section 2.9 Properties of Compounds Ionic Naming A couple more rules: Compounds involving polyatomic ions do not change the greek prefixes to indicate number. So CaCl2 is "calcium chloride", not "calcium dichloride". When a metal exists in more than one oxidation state, use the Stock system to name it, and include the oxidation state in roman numerals in parentheses after the metals' symbol. So FeO is "iron(II) oxide" and Fe2 O3 is "Iron(III) oxide". There's also an older system, using the endings -ous and name of the ion, so Fe(NO3 )2 is "Iron(II) Nitrate" not anything with an "-ide". Hydrates have "hydrate" added to the end, with a greek prefix to denote how many. So CuSO4 5H2 O is "Copper(II) sulfate pentahydrate" -ic to denote the lower, and higher oxidation states of a metal. In this system FeO is "ferrous oxide" and Fe2 O3 is "ferric oxide". Chemistry 1110/1210 Dr Eric E. Moore Section 2.1 Chemical Formulas Section 2.2 Chemical Equations Section 2.3 Energy Section 2.4 Molecular Compounds Section 2.5 Naming Compounds Section 2.6 Ionic Compounds Section 2.7 Ionic Formulas Section 2.8 Naming Ionic Compounds Section 2.9 Properties of Compounds Naming Flowchart Chemistry 1110/1210 Dr Eric E. Moore Section 2.1 Chemical Formulas Section 2.2 Chemical Equations Section 2.3 Energy Section 2.4 Molecular Compounds Section 2.5 Naming Compounds Section 2.6 Ionic Compounds Section 2.7 Ionic Formulas Section 2.8 Naming Ionic Compounds Section 2.9 Properties of Compounds Naming Review Name Cr3 (PO4 )2 Cr is Chromium PO4 is the Phosphate ion With it's charge, phosphate is PO-3 4 The total charge on the phosphate is -6 The total charge on the chromium is +6 Chromium must be in the +2 oxidation state Chromium(II) phosphate Give the formula for Vanadium(III) Silicide Vanadium is V Silicon is Si Silicon forms Si4- ions V4 Si3 Chemistry 1110/1210 Dr Eric E. Moore Section 2.1 Chemical Formulas Section 2.2 Chemical Equations Section 2.3 Energy Section 2.4 Molecular Compounds Section 2.5 Naming Compounds Section 2.6 Ionic Compounds Section 2.7 Ionic Formulas Section 2.8 Naming Ionic Compounds Section 2.9 Properties of Compounds Naming Review What is the formula for potassium perchlorate? Chemistry 1110/1210 Dr Eric E. Moore Section 2.1 Chemical Formulas Section 2.2 Chemical Equations Section 2.3 Energy Section 2.4 Molecular Compounds Section 2.5 Naming Compounds Section 2.6 Ionic Compounds Section 2.7 Ionic Formulas Section 2.8 Naming Ionic Compounds Section 2.9 Properties of Compounds Properties of ionic and molecular compounds Many properties are governed by the strength and nature of the interactions between the particles that make it up. Ionic Molecular Strength of Interactions Strong Weak Melting point High Low Hardness Hard Soft Charge on Particles Yes No Conductivity when Molten Yes No Interactions Change rapidly Change slowly Brittle Yes No The perchlorate ion is ClO- . 4 KClO4 Name NI3 N and I are nonmetals It's a molecular compound nitrogen triiodide. Name (NH4 )2 SO4 NH4 is the ammonium ion (NH+ ) 4 It's ionic. SO4 is the sulfate ion Ammonium Sulfate Chemistry 1110/1210 Dr Eric E. Moore Section 2.1 Chemical Formulas Section 2.2 Chemical Equations Section 2.3 Energy Section 2.4 Molecular Compounds Section 2.5 Naming Compounds Section 2.6 Ionic Compounds Section 2.7 Ionic Formulas Section 2.8 Naming Ionic Compounds Section 2.9 Properties of Compounds Review Name Mn2 O3 Mn is Manganese The Manganese is in the Mn3+ oxidation state Manganese(III) oxide Which compound melts at the lower temperature, NaBr or PBr3 ? One's an ionic compound, one's molecular NaBr is ionic Ionic compounds have higher melting points PBr3 has the lower melting point Give the formula for Gold(III) Fluoride Gold is Au AuF3 ...
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