CHEM 1105 S10 January 21, 2014 Chapter 3: Compounds and Formulas Today: Types of compounds: Ionic vs. covalent Naming ionic compounds Naming binary covalent compounds (two elements only) Ionic Bonding Occurs between a metal and a nonmetal element: TRANSFER of electron(s) from a metal atom to a nonmetal. Ionic bonding results in attraction between the charged ions (cations and anions) 1
Covalent Bonding The bond arises from the mutual attraction of two nuclei for the same electrons. SHARING of results Occurs between two or more nonmetal elements Metallic Bonding The bond formed between metal elements and their alloys The electron sharing differs from typical covalent bonding. Communal sharing of electrons among the metal cations Sea of electrons Explains the properties of metals and their alloys i.e., electrical conductivity 2
Ionic vs. Molecular Compounds The compound propane contains individual C 3 H 8 molecules An array of Na + ions and Cl ions (no molecules) Predicting formula of ionic compounds - Determine ions formed from element - Combine to balance charge Example: Predict the formula of the ionic compound that will form between lithium and sulphur. Li becomes Li + S becomes S 2- Li 2 S 3
Predicting charges of ions Non-metals add electrons to become ANIONS Use periodic table N 3- nitride P 3- phosphide O 2- oxide S 2- sulphide F - fluoride I - iodide Cl - chloride Br - bromide H - hydride Predicting charges of ions, continued Metals lose electrons to become CATIONS Use periodic table Group 1 Na + sodium Li + lithium K + potassium Group 2 Mg 2+ magnesium Ca 2+ calcium Group 3 Al 3+ aluminum 4
Cations, continued Group 4 Sn 2+ tin (II) Pb 2+ lead(ii) Sn 4+ tin (IV) Pb 4+ lead (IV) Transition metals: Many form more than one cation, always use roman numerals to indicate charge Naming simple ionic compounds Li 2 S Name: Name the ions Metal gets metal s name Non-metal gets modified name with -ide ending Lithium sulphide 5
Name the following ionic compounds:. NaI Mg 3 N 2 Al 2 S 3 Naming ionic compounds with type 2 metals Example: Predict the formula of the ionic compound that will form between iron and chlorine. Cl becomes Cl - Fe becomes..? Fe can form more than one cation: Fe 2+ and Fe 3+ are common ones FeCl 2 FeCl 3 Use roman numerals to denote charge of metal if the metal can form more than one cation 6
Examples Name the following ionic compounds:. SnCl 2 Cu 3 N 2 Some Common Polyatomic Ions with Their Charge Name Formula acetate C 2 H 3 O 2 carbonate CO 3 2 hydrogen carbonate (aka bicarbonate) HCO 3 hydroxide OH nitrate NO 3 nitrite NO 2 chromate CrO 4 2 dichromate Cr 2 O 7 2 ammonium NH 4 + Name hypochlorite ClO Formula chlorite ClO 2 chlorate ClO 3 perchlorate ClO 4 sulfate SO 4 2 sulfite SO 3 2 hydrogen sulfate (aka bisulfate) hydrogen sulfite (aka bisulfite) HSO 4 HSO 3 7
Polyatomic ions http://jenniferwolfchemistry.files.wordpress.co m/2012/10/polyions.pdf Examples Name the following compounds:. NaC 2 H 3 O 2 FeSO 4 Give formulas for the following compounds: potassium hydrogen carbonate cobalt (III) perchlorate 8
Naming flowchart (from book) Molecular (covalent) compounds Consist of combinations of non-metals Formulas cannot be easily predicted In this class, we will only consider binary covalent compounds (compounds consisting of only two different elements) 9
Naming molecular compounds Exceptions: Compounds with common names: Water H 2 O Ammonia NH 3 Compounds of carbon and hydrogen Organic chemistry CH 4 methane C 3 H 8 propane (not covered in this class) Naming binary molecular compounds A x B y First element gets its own name Second element gets IDE ending name (like the anions) Indicate the number of atoms of each element Mono, di, tri, tetra, penta, hexa, hepta, octa, nona, deca Do not use a prefix there is only one atom of the first element P 2 O 5 CO 2 CO 10
Examples Name the following molecular compounds:. CS 2 SBr 6 I 2 F 7 Examples Write formulas for the following: Sulfur trioxide Dinitrogen tetrahydride Diphosphorus pentasulphide 11
Hydrated ionic compounds Some compounds form a solid containing waters of hydration CaCO 3. 6H 2 O calcium carbonate hexahydrate Use same Greek prefixes with the word hydrate Acids and bases Acids Produce H + ions in aqueous solution Bases Produce OH - ions in aqueous solution Molecular compounds (liquids or gases), ionize in solution Ionic compounds with OH - as an ion (and usually a metal cation), i.e. NaOH Molecular compounds containing nitrogen NH 3 (aq) + H 2 O OH - (aq) + NH 4+ (aq) 12
Naming acids Acids that do not contain oxygen: HCl(g) hydrogen chloride (gas) HCl(aq) hydrochloric acid HBr(aq) Naming acids Acids that contain oxygen: HNO 3 (aq) nitric acid HNO 2 (aq) nitrous acid Take the name of the ion, change ate ic ite ous No hydro!!! 13