Presentation on theme: "Chemical Nomenclature “Chemical Nomenclature as we know it is born with the publication of Méthode de nomenclature chimique by Antoine-Laurent Lavoisier,"— Presentation transcript:
Chemical Nomenclature “Chemical Nomenclature as we know it is born with the publication of Méthode de nomenclature chimique by Antoine-Laurent Lavoisier, Claude-Louis Berthellot, Antoine de Fourcroy, and Guyton de Morveau. The names proposed were based on the elements origin or function. (Image produced courtesy of the Library & Information Centre, Royal Society of Chemistry)” http://www.rsc.org/chemsoc/timeline//pages/1787.html CHM 1010 PGCC Barbara Gage
Chemical Nomenclature System of rules for naming pure substances Elements – element name used even if the substance is di- or polyatomic O 2 = oxygen S 8 = sulfur Compounds - naming differs depending on whether a substance is held together primarily by ionic or covalent bonds. CHM 1010 PGCC Barbara Gage
Ions… Electrons are arranged on levels or “shells”. Atoms are most stable with 8 electrons on their outermost shell. This is often referred to as the octet rule. Number of electrons on the outer shell = Group number for elements in Groups I-VIII A (using the US convention labeling on periodic table) CHM 1010 PGCC Barbara Gage
Figure 2.10 The modern periodic table. Silberberg, Principles of Chemistry US Convention IUPAC Convention CHM 1010 PGCC Barbara Gage
Ions… To achieve the octet, atoms with more than 4 electrons on the outer shell will gain enough electrons to reach 8. Cl Group 7 7 electrons on outer shell Cl will gain 1 e -. Now #e - = 18 but #p + = 17 so the chlorine is an ion with the formula Cl 1-. CHM 1010 PGCC Barbara Gage
Ions… O Group 6 6 electrons on outer shell O will gain 2 e -. Now #e - = 10 but #p + = 8 so the oxygen is an ion with the formula O 2-. P Group 5 5 electrons on outer shell P will gain 3 e - Now #e - = 18 but #p + = 15 so the phosphorus is an ion with the formula P 3- CHM 1010 PGCC Barbara Gage
Ions… Na Group 1 1 electron on outer shell O will lose 1 e - to expose the complete inside shell. Now #e - = 10 but #p + = 11 so the sodium is an ion with the formula Na 1+. Mg Group 2 2 electrons on outer shell Mg will lose 2 e - Now #e - = 10 but #p + = 12 so the magnesium is an ion with the formula Mg 2+ CHM 1010 PGCC Barbara Gage
-- 1+ 2+3+1-2-3- Generally metals form cations and non-metals form anions.
Binary Ionic Compounds Cations (positively charged ions) and anions (negatively charged ions) will associate with each other and form a neutral binary compound to reduce energy. 1 Na + 1 Cl - NaCl 1 Ca 2+ 1 O 2- CaO 3 K + 1 N 3- K 3 N 2 Al 3+ 3 S 2- Al 2 S 3 CHM 1010 PGCC Barbara Gage
Naming binary ionic compounds The name of the cation is the same as the name of the metal. Many metal names end in -ium. The name of the anion (negatively charged ion) takes the root of the nonmetal name and adds the suffix -ide. Calcium and oxygen form calcium oxide. Aluminum and sulfur form aluminum sulfide. The name of the cation (positively charged ion) is written first, followed by that of the anion. CHM 1010 PGCC Barbara Gage
Naming Binary Ionic Compounds PROBLEM: Name the ionic compound formed from the following pairs of elements: PLAN: (a) magnesium and nitrogen SOLUTION: Use the periodic table to decide which element is the metal and which the nonmetal. The metal (cation) is named first and we use the -ide suffix on the nonmetal name root. (b) iodine and cadmium (c) strontium and fluorine(d) sulfur and potassium (a) magnesium nitride (b) cadmium iodide (c) strontium fluoride (d) potassium sulfide From Silberberg, Principles of Chemistry CHM 1010 PGCC Barbara Gage
Determining Formulas of Binary Ionic Compounds PROBLEM: Write simplest formulas for the compounds named in Sample Problem 2.5. PLAN: SOLUTION: Compounds are neutral. We find the smallest number of each ion which will produce a neutral formula. Place subscripts to the right of the element symbol. (a) Mg 2+ and N 3- ; three Mg 2+ (6+) and two N 3- (6-); Mg 3 N 2 (b) Cd 2+ and I - ; one Cd 2+ (2+) and two I - (2-); CdI 2 (c) Sr 2+ and F - ; one Sr 2+ (2+) and two F - (2-); SrF 2 (d) K + and S 2 - ; two K + (2+) and one S 2 - (2-); K 2 S CHM 1010 PGCC Barbara Gage
Binary Ionic Compounds The “B” group elements may form cations with more than one charge. To specify which cation forms a compound, a roman numeral equal to the charge is added to the cation name. Fe 2+ = iron (II) Fe 3+ = iron (III) CHM 1010 PGCC Barbara Gage
Sample Problem 2.7Determining Names and Formulas of Ionic Compounds of Elements That Form More Than One Ion PLAN: SOLUTION: Compounds are neutral. We find the smallest number of each ion which will produce a neutral formula. Use subscripts to the right of the element symbol. PROBLEM: Give the systematic names for the formulas or the formulas for the names of the following compounds: (a) tin(II) fluoride(b) Cr I 3 (c) manganese (IV) sulfide (d) CrO 3 (a) Tin (II) is Sn 2+ ; fluoride is F - ; so the formula is SnF 2. (b) The anion I is iodide( I - ); 3I - means that Cr(chromium) is +3. Cr I 3 is chromium(III) iodide (c) Manganese (IV) is Mn 2+ ; oxide is S 2-, therefore the formula is MnS 2. (d) Cr is chromium; the anion O is oxide(2-); the compound is cobalt (VI) oxide. Modified from Silberberg, Principles of Chemistry
Polyatomic Ions Some atoms form bonds that hold atoms together in a structure that has an overall charge (rather than as a neutral compound. These ions are called polyatomic ions. CO 3 2- carbonate SO 4 2- sulfate Compounds with polyatomic ions are named with the cation and anion name. Na 2 SO 4 – sodium sulfate CHM 1010 PGCC Barbara Gage
Determining Names and Formulas of Ionic Compounds Containing Polyatomic Ions PLAN: SOLUTION: Note that polyatomic ions have an overall charge so when writing a formula with more than one polyatomic unit, place the ion in a set of parentheses. PROBLEM: Give the systematic names or the formula or the formulas for the names of the following compounds: (a) Fe(ClO 4 ) 2 (b) sodium sulfite (a) ClO 4 - is perchlorate; iron must have a 2+ charge. This is iron(II) perchlorate. (b) The anion sulfite is SO 3 2- therefore you need 2 sodiums per sulfite. The formula is Na 2 SO 3.
Hydrates Some compounds have water molecules attached as part of their structure. These are termed hydrates. CuSO 4. 5H 2 O copper (II) sulfate pentahydrate CHM 1010 PGCC Barbara Gage Numerical Prefixes for Hydrates and Binary Covalent Compounds Number Prefix Number Prefix Number Prefix 1mono 2di 3tri 4tetra 5penta 6hexa 8octa 9nona 10deca
Binary Acids When certain binary gases dissolve in water they form acids with the same formula. The name is changed to add –ic acid to the anion HCl (g) HCl (aq) hydrogen chloride hydrochloric acid CHM 1010 PGCC Barbara Gage
Oxyacids Acids containing oxygen; most do not exist in the same form without water HNO 3 nitric acid HNO 2 nitrous acid H 2 SO 4 sulfuric acid H 2 CO 3 carbonic acid H 3 PO 4 phosphoric acid HC 2 H 3 O 2 or CH 3 COOH acetic acid CHM 1010 PGCC Barbara Gage
Covalent Binary Compounds Non-metals form bonds by sharing electrons rather than transferring them. The resulting bond is referred to as a covalent bond. The element farthest to the left or lower on the periodic table is generally written first. Subscripts are replaced by numerical prefixes in the name. CHM 1010 PGCC Barbara Gage
Covalent Binary Compounds CO 2 carbon dioxide N 2 Odinitrogen oxide P 2 S 5 diphosphorus pentasulfide SiCl 4 silicon tetrachloride For compounds where two vowels occur together when the prefix is added, the vowel from the prefix can be dropped (except for iodine). N 2 O 5 dinitrogen pentaoxide CHM 1010 PGCC Barbara Gage
CHM 1010 PGCC Barbara Gage Determining Names and Formulas of Binary Covalent Compounds SOLUTION: PROBLEM:(a) What is the formula of carbon disulfide? (b) What is the name of PCl 5 ? (a) Carbon is C, sulfide is sulfur S and di-means 2 - CS 2. (b) P is phosphorus, Cl is chloride, the prefix for 5 is penta-. Phosphorus pentachloride.