Naming & Calculating Chemical Compounds Unit3 – Lecture 2

Recap – Bonding Occurs… …to fill the outer level of electrons of elements you can predict bonding by observing trends on the periodic table: type of element: metals, non metals, etc valence electrons: for lewis diagrams oxidation #: criss-cross method

Counting Atoms A Chemical Formula shows how many of which atoms are in a molecule A Subscript is a number placed below and behind a symbol to show how many of which atoms are present H2O

Counting Atoms A Coefficient is placed in front of a molecule to show more than one molecule 3H2O

H2 N2 O2 F2 I2 Cl2 Br2 Counting Atoms A Diatomic Molecule shows two atoms of the same nonmetal (usually in gas form) that have bonded together Reactive nonmetals will bond with one another if no other substance is available for bonding

Ca(OH)2 NH4Cl Polyatomic Ions A group of atoms that behave as one atom Keep together as a unit Listed on p. 619 If more than one polyatomic ion is present in a molecule, parentheses set it apart Still use a subscript to show how many Ca(OH)2 NH4Cl

Oxidation Numbers A positive or negative sign used to show what type of ion is formed after an atom has gained or lost enough electrons to be chemically stable Written like a charge sign (upper right) Always included with a list of polyatomic ions

BASE OXIDATION NUMBERS BY GROUP +1 0 +2 +3 ±4 -3 -2 -1 USE ROMAN NUMERALS

Oxidation #s – cont’d Transition metals have more than one oxidation number!!!! Fe[III] = Fe+3 = Iron with +3 oxidation number Fe[II] = Fe+2 = Iron with +2 oxidation number Mn[II] = Mn+2 = Manganese with +2 oxidation number Mn[III] = Mn+3 = Manganese with +3 oxidation number

Making Formulae – the “Criss-Cross” Method cation first – write element & oxidation # anion next – write element & oxidation # without the + or – sign write the oxidation # from one symbol on the other as a subscript remember to add parentheses around polyatomic ions don’t write the #1, it is implied reduce any evenly-divisible subscripts

Practice What is the correct formula for a bond between… Carbon and Hydrogen? CH C2H2 CH3 C2H3 CH4 Sodium and Nitrogen? NaN Na2N2 Na3N Na2N3 Na3N4 Calcium and Chlorine? CaCl Ca2Cl2 Ca2Cl CaCl2 Ca3Cl4

Practice – cont’d What is the correct formula for a bond between… Sodium and Hydroxide (OH) ? [hint: figure out the leftover charge from combining an oxygen an a hydrogen] NaOH Na(OH)2 Na(OH)3 Na2(OH)3 Na(OH)4 Aluminum and Sulfate (SO4) ? AlSO4 Al2(SO4)2 Al2(SO4)3 Al3(SO4)3 Al(SO4)4

Binomial Nomenclature Naming a two-part name Used to differentiate between Fluorine (an element) and Fluoride (part of a compound) Never change the name of a Polyatomic Ion Big difference between Sulfide and Sulfite

Naming Ionic Compounds List the positive ion (or metal) first ***Use Roman Numerals to show the Oxidation number of a transition metal Name the negative ion (or nonmetal), changing the ending to –ide “Oxide” “Sulfide” “Phosphide” Ex: FeO / Fe2O3 = Iron II Oxide / Iron III Oxide

Naming Polyatomic Compounds Compound is polyatomic if there are more than 2 elements You will be given the names for common polyatomics. Still only 2 words in the name first term = positive ion name second term = negative ion name if second term is NOT a polyatomic, change ending to -ide if the second term is a negative polyatomic, do NOT change the ending

Naming Covalent Compounds Prefixes are used to show how many of which atoms = number terms from Greek / Latin Write the name of the cation [or most positive] only add a prefix for the first atom if there is more than one Write the name of the anion [or most negative] add a prefix to tell how many are present change the ending to -ide

Covalent Compounds Prefixes are used to show how many of which atoms Prefixes are number-words from Greek & Latin Write the name of the first atom Add a prefix only if there is more than one of the first Write the name of the second atom Add a prefix showing how many of the second are present Change the ending to -ide

Numbering Prefixes 1 – Mono- 2 – Di- 3 – Tri- 4 – Tetra-, 5 – Penta- 6 – Hexa- 7 – Hepta- 8 – Octa- 9 – Nona- 10 – Deka-

What is the name for N2O4? Nitrogen Oxide Dinitrogen Oxide Dinitrogen Dioxide Dinitrogen Tetraoxide Nioxx (Nioxalate)

What is the name for Na2S? Sodium Sulfide Sodium Sulfite Sodium Sulfate Disodium Sulfide Disodium Sulfate

What is the name for CO2? Carbon Oxide Carbon Dioxide Monocarbon Oxide Monocarbon Dioxide Mi-Bref (B-hot)

What is the name for (NH4)2O? Nitrogen Hydrogen Oxide Mononitrogen Tetrahydrogen Oxide Ammonium Oxide Diammonium Oxide Ammonium Oxalate

Practice What is the name for N2O4? What is the name for Na2S? non-metal + non-metal…so covalent Dinitrogen Tetraoxide What is the name for Na2S? metal + non-metal = ionic Sodium Sulfide What is the name for CO2? non-metal + non-metal = covalent Carbon Dioxide

Practice – cont’d What is the name for (NH4)2O? [hint: you need to know what (NH4) is…] Nitrogen Hydrogen Oxide Mononitrogen Tetrahydrogen Oxide Ammonium Oxide Diammonium Oxide Ammonium Oxalate CORRECT!!!!

Practice – cont’d Al2S3 CrO Lead (II) oxide PbO2 (NH4)2S Ca(OH)2 Iron (II) cyanide Fe(NO3)3 Aluminum sulfide Chromium (II) oxide PbO Lead (IV) oxide Ammonium sulfide Calcium hydroxide Fe(CN)2 Iron (III) nitrate