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(Section 2.8) Chemical Nomenclature: Names and Formula (Section 2.8) Inorganic Compounds: The naming of ionic and molecular inorganic compounds should be review for you! You are expected to be proficient in inorganic nomenclature and to know some simple organic nomenclature. This is essential for success in future topics covered in general chemistry! Let’s start with Binary Ionic Compounds: Both Cation & Anion Monatomic • Cations are formed when an atom LOSES electrons (oxidation). lost e– (to anion) • Anions are formed when an atom GAINS electrons (reduction). gained e– (from cation) For all ionic compounds, the name and formula lists the cation first and the anion second. For binary ionic compounds the name of the cation is the same as the name of the metal. The anion is named by adding the suffix -ide to the root of the nonmetal name. Formulas of ionic compounds are empirical formulas, they reflect the smallest whole number ratio of cations to anions that results in a net charge of zero. LiF is called lithium fluoride. Larson-Foothill College 1 Using the Periodic Table to Determine Charges of Most Main Group Monatomic Cations and Anions (Octet Rule) • • – – – – – Metals form cations: They lose their valence shell electrons. – Group 1A : lose how many e–? – Group 2A: lose how many e–? – Metals of group 3A: lose how many e–? Nonmetals form anions: They gain electrons to fill their valence shell. Group 4A nonmetal: gain how many e–? Group 5A nonmetals: gain how many e–? Group 6A nonmetals: gain how many e–? Group 7A: gain how many e–? H when bonded to a metal: gains how many e–? Larson-Foothill College What’s the formula of: Aluminum Bromide Calcium Phosphide Name the following: LiH Ca2C 2 Some Common Monatomic Ions What’s the formula of: Chromium (II) Bromide Cadmium sulfide Name the following: Pb3N2 Ag2O Ni2+ Most main-group elements form one monatomic ion. Most transition elements form two monatomic ions. When naming these, you MUST include the charge in the name. We will do this using Roman Numerals: Fe2+ is called iron (II) in a compound name. Common transition elements that form only one ion-MEMORIZE these. In naming these, a Roman Numeral is NOT used: Zn2+ is called zinc in a compound name. Larson-Foothill College 3 Systematic naming of a series of oxoanions: No. of O atoms Prefix per hypo Root Suffix root ate ClO4- Example perchlorate root ate ClO3- chlorate root ite ClO2- chlorite root ite ClO- hypochlorite Models illustrating the covalent bonding within phosphate and hydrogen phosphate ions: What’s the formula of: Iron (II) Phosphate Iron (II) Hydrogen Phosphate Ammonium sulfate Name the following: (Endings Matter!) Cu(NO3)2 Cu(NO2)2 Cu3N2 Larson-Foothill College 4 Hydrates Hydrates are inorganic salts (ionic compounds) containing water molecules combined in a definite ratio as an integral part of the crystal structure. Hydrates are said to contain water of hydration. The specific number of water molecules in each formula unit is indicated using Greek numerical prefixes: Number Prefix Number Prefix Number Prefix 1 mono- 4 tetra- 8 octa- 2 di- 5 penta- 9 nona- 3 tri- 6 hexa- 10 deca- 7 hepta- Example: Epsom Salts is magnesium sulfate heptahydrate. The formula is written as MgSO4•7H2O or MgSO4•(H2O)7 Heating a hydrate can remove the waters of hydration; the process can then be reversed when water is present, such as in air with high humidity. A colorful example is cobalt (II) Chloride which turns from blue to red upon hydration, and can therefore be used as a water indicator. Expose to moisture Anhydrous cobalt (II) chloride What’s the formula? Hydrated cobalt (II) chloride hexahydrate What’s the formula? Larson-Foothill College 5 Naming Binary Covalent Compounds • • A binary covalent compound is typically formed by the combination of two non-metals. Some of these compounds are very common and have trivial names, eg., H2O is water and NH3 is ammonia. For a binary covalent compound, the element with the lower electronegativity is generally first in the name and formula. Its name remains unchanged. • • The element that is second is named using the root with the suffix –ide. Compounds are named using Greek numerical prefixes to indicate the number of atoms of each element present with the following two exceptions: (1) prefixes are generally not used for compounds with hydrogen listed as the first element in the formula (2) the first element in the name has a prefix only when more than one atom of it is present (in other words, mono is not used for the first element.) • When the element is oxygen and the prefix ends in a or o the, a or o of the prefix is dropped for ease of pronunciation. For example, mono-oxide becomes monoxide and tetra-oxide becomes tetroxide. What’s the formula of: dichlorine heptoxide Hydrogen chloride Hydrogen chloride is a colorless gas (boiling point -85°C) that consists molecules containing hydrogen and chlorine connected by a polar covalent bond. Hydrogen chloride forms corrosive hydrochloric acid on contact with water found in body tissues. Inhalation of the fumes can cause coughing, chocking, inflammations of the nose, throat, and upper respiratory tract. 0 3 1 acid Name the following: H 2S CCl4 Larson-Foothill College 6 Naming Acids • Litmus Paper Red = Acid In the Arrhenius definition, an acid is a substance that + produces hydrogen (H ) ions when dissolved in water. An example is hydrochloric acid: HCl(aq) –> H+(aq) + Cl–(aq) HCl(g) However, not all compounds that contain hydrogen behave as acids (e.g. PH3 and CH4 are not acids). Acids generally have hydrogen written first in their formula. HCl(aq) There are two types of acids important for Chemistry 1A: 1) Binary acid solutions form when certain gaseous compounds dissolve in water. For example, when gaseous hydrogen chloride (HCl) dissolves in water, it forms a solution called hydrochloric acid. Prefix hydro- + anion nonmetal root + suffix -ic + the word acid hydro + chlor + ic + acid hydrochloric acid 2) Oxoacid names are similar to those of the oxoanions, except for two suffix changes: -ate in the anion becomes –ic in the acid -ite in the anion becomes –ous in the acid The oxoanion prefixes hypo- and per- are retained. Thus, BrO4– is perbromate, and HBrO4 is perbromic acid; IO2– is iodite, and HIO2 is iodous acid. What’s the formula of: Hydrosulfuric acid Sulfuric acid Name the following: H2CrO4(aq) Larson-Foothill College 7 Naming Some Simple Organic Compounds • Straight-Chain Alkanes: Hydrocarbons are compounds that contain only carbon and hydrogen. Alkanes: simplest type of hydrocarbon, all bonds are single Alkanes are named using a root name followed by the suffix –ane. methane ethane propane • In November 1776, methane was first scientifically identified by Italian physicist Alessandro Volta in the marshes of Lake Maggiore having been inspired to search for the substance after reading a paper written by Benjamin Franklin about "flammable air". Volta captured the gas rising from the marsh, and by 1778 had isolated the pure gas. He also demonstrated means to ignite the gas with an electric spark. Alcohols: contain the –OH functional* group, covalently bonded to a carbon atom (this is NOT a hydroxide). Alcohols are named using a root name followed by the suffix –ol. Vast amounts of methane are locked up inside icelike frozen clathrates in permafrost and the ocean depths. When these clathrates are brought to the surface, methane gas is released. methanol (also called methyl alcohol) methyl CH3– ethanol (also called ethyl alcohol) ethyl CH3CH2– *Functional Group: An atom or group of atoms that imparts characteristic properties to an organic compound. Larson-Foothill College 8 Naming Some Simple Organic Compounds • Carboxylic acids: contain the –COOH functional group Carboxylic acids are named using a root name followed by the suffix –oic acid. methanoic acid The common name, formic acid, is usually used. ethanoic acid What is the common name that is usually used? • When ethanol reacts with oxygen it forms a weak acid called ethanoic acid. In an open bottle of beer or wine, the reaction happens naturally in the presence of bacteria, and it is ethanoic acid that can make beer or wine taste sour. Ethanoic acid is found in vinegar ("vinegar" is old french for “sour wine"). Vinegar is used as a food flavoring and preservative. Amines: contain the -NHx functional group where x can be 0, 1, or 2. (chemically similar to NH3) Amines are named using a root name followed by the suffix –amine. Greek numerical prefixes are included as illustrated below. methylamine dimethylamine trimethylamine Amines are ubiquitous in biology. The breakdown of amino acids releases amines, famously in the case of decaying fish which smell of trimethylamine. Many neurotransmitters are amines, including epinephrine, dopamine, serotonin and histamine. ethylamine Histamine Larson-Foothill College 9